hypothesis and theories

Hypothesis vs. Theory

A hypothesis is either a suggested explanation for an observable phenomenon, or a reasoned prediction of a possible causal correlation among multiple phenomena. In science , a theory is a tested, well-substantiated, unifying explanation for a set of verified, proven factors. A theory is always backed by evidence; a hypothesis is only a suggested possible outcome, and is testable and falsifiable.

Comparison chart

Examples of theory and hypothesis.

Theory: Einstein's theory of relativity is a theory because it has been tested and verified innumerable times, with results consistently verifying Einstein's conclusion. However, simply because Einstein's conclusion has become a theory does not mean testing of this theory has stopped; all science is ongoing. See also the Big Bang theory , germ theory , and climate change .

Hypothesis: One might think that a prisoner who learns a work skill while in prison will be less likely to commit a crime when released. This is a hypothesis, an "educated guess." The scientific method can be used to test this hypothesis, to either prove it is false or prove that it warrants further study. (Note: Simply because a hypothesis is not found to be false does not mean it is true all or even most of the time. If it is consistently true after considerable time and research, it may be on its way to becoming a theory.)

This video further explains the difference between a theory and a hypothesis:

Common Misconception

People often tend to say "theory" when what they're actually talking about is a hypothesis. For instance, "Migraines are caused by drinking coffee after 2 p.m. — well, it's just a theory, not a rule."

This is actually a logically reasoned proposal based on an observation — say 2 instances of drinking coffee after 2 p.m. caused a migraine — but even if this were true, the migraine could have actually been caused by some other factors.

Because this observation is merely a reasoned possibility, it is testable and can be falsified — which makes it a hypothesis, not a theory.

What is a Scientific Hypothesis? - LiveScience
Wikipedia:Scientific theory

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Comments: Hypothesis vs Theory

Anonymous comments (2).

October 11, 2013, 1:11pm "In science, a theory is a well-substantiated, unifying explanation for a set of verified, proven hypotheses." But there's no such thing as "proven hypotheses". Hypotheses can be tested/falsified, they can't be "proven". That's just not how science works. Logical deductions based on axioms can be proven, but not scientific hypotheses. On top of that I find it somewhat strange to claim that a theory doesn't have to be testable, if it's built up from hypotheses, which DO have to be testable... — 80.✗.✗.139

May 6, 2014, 11:45pm "Evolution is a theory, not a fact, regarding the origin of living things." this statement is poorly formed because it implies that a thing is a theory until it gets proven and then it is somehow promoted to fact. this is just a misunderstanding of what the words mean, and of how science progresses generally. to say that a theory is inherently dubious because "it isn't a fact" is pretty much a meaningless statement. no expression which qualified as a mere fact could do a very good job of explaining the complicated process by which species have arisen on Earth over the last billion years. in fact, if you claimed that you could come up with such a single fact, now THAT would be dubious! everything we observe in nature supports the theory of evolution, and nothing we observe contradicts it. when you can say this about a theory, it's a pretty fair bet that the theory is correct. — 71.✗.✗.151

Accuracy vs Precision
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“Theory” vs. “Hypothesis”: What Is The Difference?

Chances are you’ve heard of the TV show The Big Bang Theory . Lots of people love this lighthearted sitcom for its quirky characters and their relationships, but others haven’t even given the series a chance for one reason: they don’t like science and assume the show is boring.

However, it only takes a few seconds with Sheldon and Penny to disprove this assumption and realize that this theory ab0ut The Big Bang Theory is wrong—it isn’t a scientific snoozefest.

But wait: is it a theory or a hypothesis about the show that leads people astray? And would the actual big bang theory— the one that refers to the beginning of the universe—mean the same thing as a big bang hypothesis ?

Let’s take a closer look at theory and hypothesis to nail down what they mean.

What does theory mean?

As a noun, a theory is a group of tested general propositions “commonly regarded as correct, that can be used as principles of explanation and prediction for a class of phenomena .” This is what is known as a scientific theory , which by definition is “an understanding that is based on already tested data or results .” Einstein’s theory of relativity and the theory of evolution are both examples of such tested propositions .

Theory is also defined as a proposed explanation you might make about your own life and observations, and it’s one “whose status is still conjectural and subject to experimentation .” For example: I’ve got my own theories about why he’s missing his deadlines all the time. This example refers to an idea that has not yet been proven.

There are other uses of the word theory as well.

In this example, theory is “a body of principles or theorems belonging to one subject.” It can be a branch of science or art that deals with its principles or methods .
For example: when she started to follow a new parenting theory based on a trendy book, it caused a conflict with her mother, who kept offering differing opinions .

First recorded in 1590–1600, theory originates from the Late Latin theōria , which stems from the Greek theōría. Synonyms for theory include approach , assumption , doctrine , ideology , method , philosophy , speculation , thesis , and understanding .

What does hypothesis mean?

Hypothesis is a noun that means “a proposition , or set of propositions, set forth as an explanation” that describe “some specified group of phenomena.” Sounds familiar to theory , no?

But, unlike a theory , a scientific hypothesis is made before testing is done and isn’t based on results. Instead, it is the basis for further investigation . For example: her working hypothesis is that this new drug also has an unintended effect on the heart, and she is curious what the clinical trials will show .

Hypothesis also refers to “a proposition assumed as a premise in an argument,” or “mere assumption or guess.” For example:

She decided to drink more water for a week to test out her hypothesis that dehydration was causing her terrible headaches.
After a night of her spouse’s maddening snoring, she came up with the hypothesis that sleeping on his back was exacerbating the problem.

Hypothesis was first recorded around 1590–1600 and originates from the Greek word hypóthesis (“basis, supposition”). Synonyms for hypothesis include: assumption , conclusion , conjecture , guess , inference , premise , theorem , and thesis .

How to use each

Although theory in terms of science is used to express something based on extensive research and experimentation, typically in everyday life, theory is used more casually to express an educated guess.

So in casual language, theory and hypothesis are more likely to be used interchangeably to express an idea or speculation .

In most everyday uses, theory and hypothesis convey the same meaning. For example:

Her opinion is just a theory , of course. She’s just guessing.
Her opinion is just a hypothesis , of course. She’s just guessing.

It’s important to remember that a scientific theory is different. It is based on tested results that support or substantiate it, whereas a hypothesis is formed before the research.

For example:

His hypothesis for the class science project is that this brand of plant food is better than the rest for helping grass grow.
After testing his hypothesis , he developed a new theory based on the experiment results: plant food B is actually more effective than plant food A in helping grass grow.

In these examples, theory “doesn’t mean a hunch or a guess,” according to Kenneth R. Miller, a cell biologist at Brown University. “A theory is a system of explanations that ties together a whole bunch of facts. It not only explains those facts, but predicts what you ought to find from other observations and experiments.”

So if you have a concept that is based on substantiated research, it’s a theory .

But if you’re working off of an assumption that you still need to test, it’s a hypothesis .

So remember, first comes a hypothesis , then comes theory . Now who’s ready for a Big Bang Theory marathon?

Now that you’ve theorized and hypothesized through this whole article … keep testing your judgment (Or is it judgement?). Find out the correct spelling here!

Or find out the difference between these two common issues below!

WATCH: "Lethologica" vs. "Lethonomia": What's The Difference?

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Home » What is a Hypothesis – Types, Examples and Writing Guide

What is a Hypothesis – Types, Examples and Writing Guide

Table of Contents

Definition:

Hypothesis is an educated guess or proposed explanation for a phenomenon, based on some initial observations or data. It is a tentative statement that can be tested and potentially proven or disproven through further investigation and experimentation.

Hypothesis is often used in scientific research to guide the design of experiments and the collection and analysis of data. It is an essential element of the scientific method, as it allows researchers to make predictions about the outcome of their experiments and to test those predictions to determine their accuracy.

Types of Hypothesis

Types of Hypothesis are as follows:

Research Hypothesis

A research hypothesis is a statement that predicts a relationship between variables. It is usually formulated as a specific statement that can be tested through research, and it is often used in scientific research to guide the design of experiments.

Null Hypothesis

The null hypothesis is a statement that assumes there is no significant difference or relationship between variables. It is often used as a starting point for testing the research hypothesis, and if the results of the study reject the null hypothesis, it suggests that there is a significant difference or relationship between variables.

Alternative Hypothesis

An alternative hypothesis is a statement that assumes there is a significant difference or relationship between variables. It is often used as an alternative to the null hypothesis and is tested against the null hypothesis to determine which statement is more accurate.

Directional Hypothesis

A directional hypothesis is a statement that predicts the direction of the relationship between variables. For example, a researcher might predict that increasing the amount of exercise will result in a decrease in body weight.

Non-directional Hypothesis

A non-directional hypothesis is a statement that predicts the relationship between variables but does not specify the direction. For example, a researcher might predict that there is a relationship between the amount of exercise and body weight, but they do not specify whether increasing or decreasing exercise will affect body weight.

Statistical Hypothesis

A statistical hypothesis is a statement that assumes a particular statistical model or distribution for the data. It is often used in statistical analysis to test the significance of a particular result.

Composite Hypothesis

A composite hypothesis is a statement that assumes more than one condition or outcome. It can be divided into several sub-hypotheses, each of which represents a different possible outcome.

Empirical Hypothesis

An empirical hypothesis is a statement that is based on observed phenomena or data. It is often used in scientific research to develop theories or models that explain the observed phenomena.

Simple Hypothesis

A simple hypothesis is a statement that assumes only one outcome or condition. It is often used in scientific research to test a single variable or factor.

Complex Hypothesis

A complex hypothesis is a statement that assumes multiple outcomes or conditions. It is often used in scientific research to test the effects of multiple variables or factors on a particular outcome.

Applications of Hypothesis

Hypotheses are used in various fields to guide research and make predictions about the outcomes of experiments or observations. Here are some examples of how hypotheses are applied in different fields:

Science : In scientific research, hypotheses are used to test the validity of theories and models that explain natural phenomena. For example, a hypothesis might be formulated to test the effects of a particular variable on a natural system, such as the effects of climate change on an ecosystem.
Medicine : In medical research, hypotheses are used to test the effectiveness of treatments and therapies for specific conditions. For example, a hypothesis might be formulated to test the effects of a new drug on a particular disease.
Psychology : In psychology, hypotheses are used to test theories and models of human behavior and cognition. For example, a hypothesis might be formulated to test the effects of a particular stimulus on the brain or behavior.
Sociology : In sociology, hypotheses are used to test theories and models of social phenomena, such as the effects of social structures or institutions on human behavior. For example, a hypothesis might be formulated to test the effects of income inequality on crime rates.
Business : In business research, hypotheses are used to test the validity of theories and models that explain business phenomena, such as consumer behavior or market trends. For example, a hypothesis might be formulated to test the effects of a new marketing campaign on consumer buying behavior.
Engineering : In engineering, hypotheses are used to test the effectiveness of new technologies or designs. For example, a hypothesis might be formulated to test the efficiency of a new solar panel design.

How to write a Hypothesis

Here are the steps to follow when writing a hypothesis:

Identify the Research Question

The first step is to identify the research question that you want to answer through your study. This question should be clear, specific, and focused. It should be something that can be investigated empirically and that has some relevance or significance in the field.

Conduct a Literature Review

Before writing your hypothesis, it’s essential to conduct a thorough literature review to understand what is already known about the topic. This will help you to identify the research gap and formulate a hypothesis that builds on existing knowledge.

Determine the Variables

The next step is to identify the variables involved in the research question. A variable is any characteristic or factor that can vary or change. There are two types of variables: independent and dependent. The independent variable is the one that is manipulated or changed by the researcher, while the dependent variable is the one that is measured or observed as a result of the independent variable.

Formulate the Hypothesis

Based on the research question and the variables involved, you can now formulate your hypothesis. A hypothesis should be a clear and concise statement that predicts the relationship between the variables. It should be testable through empirical research and based on existing theory or evidence.

Write the Null Hypothesis

The null hypothesis is the opposite of the alternative hypothesis, which is the hypothesis that you are testing. The null hypothesis states that there is no significant difference or relationship between the variables. It is important to write the null hypothesis because it allows you to compare your results with what would be expected by chance.

Refine the Hypothesis

After formulating the hypothesis, it’s important to refine it and make it more precise. This may involve clarifying the variables, specifying the direction of the relationship, or making the hypothesis more testable.

Examples of Hypothesis

Here are a few examples of hypotheses in different fields:

Psychology : “Increased exposure to violent video games leads to increased aggressive behavior in adolescents.”
Biology : “Higher levels of carbon dioxide in the atmosphere will lead to increased plant growth.”
Sociology : “Individuals who grow up in households with higher socioeconomic status will have higher levels of education and income as adults.”
Education : “Implementing a new teaching method will result in higher student achievement scores.”
Marketing : “Customers who receive a personalized email will be more likely to make a purchase than those who receive a generic email.”
Physics : “An increase in temperature will cause an increase in the volume of a gas, assuming all other variables remain constant.”
Medicine : “Consuming a diet high in saturated fats will increase the risk of developing heart disease.”

Purpose of Hypothesis

The purpose of a hypothesis is to provide a testable explanation for an observed phenomenon or a prediction of a future outcome based on existing knowledge or theories. A hypothesis is an essential part of the scientific method and helps to guide the research process by providing a clear focus for investigation. It enables scientists to design experiments or studies to gather evidence and data that can support or refute the proposed explanation or prediction.

The formulation of a hypothesis is based on existing knowledge, observations, and theories, and it should be specific, testable, and falsifiable. A specific hypothesis helps to define the research question, which is important in the research process as it guides the selection of an appropriate research design and methodology. Testability of the hypothesis means that it can be proven or disproven through empirical data collection and analysis. Falsifiability means that the hypothesis should be formulated in such a way that it can be proven wrong if it is incorrect.

In addition to guiding the research process, the testing of hypotheses can lead to new discoveries and advancements in scientific knowledge. When a hypothesis is supported by the data, it can be used to develop new theories or models to explain the observed phenomenon. When a hypothesis is not supported by the data, it can help to refine existing theories or prompt the development of new hypotheses to explain the phenomenon.

When to use Hypothesis

Here are some common situations in which hypotheses are used:

In scientific research , hypotheses are used to guide the design of experiments and to help researchers make predictions about the outcomes of those experiments.
In social science research , hypotheses are used to test theories about human behavior, social relationships, and other phenomena.
I n business , hypotheses can be used to guide decisions about marketing, product development, and other areas. For example, a hypothesis might be that a new product will sell well in a particular market, and this hypothesis can be tested through market research.

Characteristics of Hypothesis

Here are some common characteristics of a hypothesis:

Testable : A hypothesis must be able to be tested through observation or experimentation. This means that it must be possible to collect data that will either support or refute the hypothesis.
Falsifiable : A hypothesis must be able to be proven false if it is not supported by the data. If a hypothesis cannot be falsified, then it is not a scientific hypothesis.
Clear and concise : A hypothesis should be stated in a clear and concise manner so that it can be easily understood and tested.
Based on existing knowledge : A hypothesis should be based on existing knowledge and research in the field. It should not be based on personal beliefs or opinions.
Specific : A hypothesis should be specific in terms of the variables being tested and the predicted outcome. This will help to ensure that the research is focused and well-designed.
Tentative: A hypothesis is a tentative statement or assumption that requires further testing and evidence to be confirmed or refuted. It is not a final conclusion or assertion.
Relevant : A hypothesis should be relevant to the research question or problem being studied. It should address a gap in knowledge or provide a new perspective on the issue.

Advantages of Hypothesis

Hypotheses have several advantages in scientific research and experimentation:

Guides research: A hypothesis provides a clear and specific direction for research. It helps to focus the research question, select appropriate methods and variables, and interpret the results.
Predictive powe r: A hypothesis makes predictions about the outcome of research, which can be tested through experimentation. This allows researchers to evaluate the validity of the hypothesis and make new discoveries.
Facilitates communication: A hypothesis provides a common language and framework for scientists to communicate with one another about their research. This helps to facilitate the exchange of ideas and promotes collaboration.
Efficient use of resources: A hypothesis helps researchers to use their time, resources, and funding efficiently by directing them towards specific research questions and methods that are most likely to yield results.
Provides a basis for further research: A hypothesis that is supported by data provides a basis for further research and exploration. It can lead to new hypotheses, theories, and discoveries.
Increases objectivity: A hypothesis can help to increase objectivity in research by providing a clear and specific framework for testing and interpreting results. This can reduce bias and increase the reliability of research findings.

Limitations of Hypothesis

Some Limitations of the Hypothesis are as follows:

Limited to observable phenomena: Hypotheses are limited to observable phenomena and cannot account for unobservable or intangible factors. This means that some research questions may not be amenable to hypothesis testing.
May be inaccurate or incomplete: Hypotheses are based on existing knowledge and research, which may be incomplete or inaccurate. This can lead to flawed hypotheses and erroneous conclusions.
May be biased: Hypotheses may be biased by the researcher’s own beliefs, values, or assumptions. This can lead to selective interpretation of data and a lack of objectivity in research.
Cannot prove causation: A hypothesis can only show a correlation between variables, but it cannot prove causation. This requires further experimentation and analysis.
Limited to specific contexts: Hypotheses are limited to specific contexts and may not be generalizable to other situations or populations. This means that results may not be applicable in other contexts or may require further testing.
May be affected by chance : Hypotheses may be affected by chance or random variation, which can obscure or distort the true relationship between variables.

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1.2: Theories, Hypotheses and Models

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For the purpose of this textbook (and science in general), we introduce a distinction in what we mean by “theory”, “hypothesis”, and by “model”. We will consider a “theory” to be a set of statements (or an equation) that gives us a broad description, applicable to several phenomena and that allows us to make verifiable predictions. For example, Chloë’s Theory ( $t \propto \sqrt{h}$ ) can be considered a theory. Specifically, we do not use the word theory in the context of “I have a theory about this...”

A “hypothesis” is a consequence of the theory that one can test. From Chloë’s Theory, we have the hypothesis that an object will take $\sqrt{2}$ times longer to fall from $1\:\text{m}$ than from $2\:\text{m}$ . We can formulate the hypothesis based on the theory and then test that hypothesis. If the hypothesis is found to be invalidated by experiment, then either the theory is incorrect, or the hypothesis is not consistent with the theory.

A “model” is a situation-specific description of a phenomenon based on a theory , that allows us to make a specific prediction. Using the example from the previous section, our theory would be that the fall time of an object is proportional to the square root of the drop height, and a model would be applying that theory to describe a tennis ball falling by $4.2$ m. From the model, we can form a testable hypothesis of how long it will take the tennis ball to fall that distance. It is important to note that a model will almost always be an approximation of the theory applied to describe a particular phenomenon. For example, if Chloë’s Theory is only valid in vacuum, and we use it to model the time that it take for an object to fall at the surface of the Earth, we may find that our model disagrees with experiment. We would not necessarily conclude that the theory is invalidated, if our model did not adequately apply the theory to describe the phenomenon (e.g. by forgetting to include the effect of air drag).

This textbook will introduce the theories from Classical Physics, which were mostly established and tested between the seventeenth and nineteenth centuries. We will take it as given that readers of this textbook are not likely to perform experiments that challenge those well-established theories. The main challenge will be, given a theory, to define a model that describes a particular situation, and then to test that model. This introductory physics course is thus focused on thinking of “doing physics” as the task of correctly modeling a situation.

Emma's Thoughts

What’s the difference between a model and a theory?

“Model” and “Theory” are sometimes used interchangeably among scientists. In physics, it is particularly important to distinguish between these two terms. A model provides an immediate understanding of something based on a theory.

For example, if you would like to model the launch of your toy rocket into space, you might run a computer simulation of the launch based on various theories of propulsion that you have learned. In this case, the model is the computer simulation, which describes what will happen to the rocket. This model depends on various theories that have been extensively tested such as Newton’s Laws of motion, Fluid dynamics, etc.

“Model”: Your homemade rocket computer simulation
“Theory”: Newton’s Laws of motion, Fluid dynamics

With this analogy, we can quickly see that the “model” and “theory” are not interchangeable. If they were, we would be saying that all of Newton’s Laws of Motion depend on the success of your piddly toy rocket computer simulation!

Exercise $\PageIndex{2}$

Models cannot be scientifically tested, only theories can be tested.

Want to create or adapt books like this? Learn more about how Pressbooks supports open publishing practices.

Developing a Hypothesis

Rajiv S. Jhangiani; I-Chant A. Chiang; Carrie Cuttler; and Dana C. Leighton

Learning Objectives

Distinguish between a theory and a hypothesis.
Discover how theories are used to generate hypotheses and how the results of studies can be used to further inform theories.
Understand the characteristics of a good hypothesis.

Theories and Hypotheses

Before describing how to develop a hypothesis, it is important to distinguish between a theory and a hypothesis. A theory is a coherent explanation or interpretation of one or more phenomena. Although theories can take a variety of forms, one thing they have in common is that they go beyond the phenomena they explain by including variables, structures, processes, functions, or organizing principles that have not been observed directly. Consider, for example, Zajonc’s theory of social facilitation and social inhibition (1965) [1] . He proposed that being watched by others while performing a task creates a general state of physiological arousal, which increases the likelihood of the dominant (most likely) response. So for highly practiced tasks, being watched increases the tendency to make correct responses, but for relatively unpracticed tasks, being watched increases the tendency to make incorrect responses. Notice that this theory—which has come to be called drive theory—provides an explanation of both social facilitation and social inhibition that goes beyond the phenomena themselves by including concepts such as “arousal” and “dominant response,” along with processes such as the effect of arousal on the dominant response.

Outside of science, referring to an idea as a theory often implies that it is untested—perhaps no more than a wild guess. In science, however, the term theory has no such implication. A theory is simply an explanation or interpretation of a set of phenomena. It can be untested, but it can also be extensively tested, well supported, and accepted as an accurate description of the world by the scientific community. The theory of evolution by natural selection, for example, is a theory because it is an explanation of the diversity of life on earth—not because it is untested or unsupported by scientific research. On the contrary, the evidence for this theory is overwhelmingly positive and nearly all scientists accept its basic assumptions as accurate. Similarly, the “germ theory” of disease is a theory because it is an explanation of the origin of various diseases, not because there is any doubt that many diseases are caused by microorganisms that infect the body.

A hypothesis , on the other hand, is a specific prediction about a new phenomenon that should be observed if a particular theory is accurate. It is an explanation that relies on just a few key concepts. Hypotheses are often specific predictions about what will happen in a particular study. They are developed by considering existing evidence and using reasoning to infer what will happen in the specific context of interest. Hypotheses are often but not always derived from theories. So a hypothesis is often a prediction based on a theory but some hypotheses are a-theoretical and only after a set of observations have been made, is a theory developed. This is because theories are broad in nature and they explain larger bodies of data. So if our research question is really original then we may need to collect some data and make some observations before we can develop a broader theory.

Theories and hypotheses always have this if-then relationship. “ If drive theory is correct, then cockroaches should run through a straight runway faster, and a branching runway more slowly, when other cockroaches are present.” Although hypotheses are usually expressed as statements, they can always be rephrased as questions. “Do cockroaches run through a straight runway faster when other cockroaches are present?” Thus deriving hypotheses from theories is an excellent way of generating interesting research questions.

But how do researchers derive hypotheses from theories? One way is to generate a research question using the techniques discussed in this chapter and then ask whether any theory implies an answer to that question. For example, you might wonder whether expressive writing about positive experiences improves health as much as expressive writing about traumatic experiences. Although this question is an interesting one on its own, you might then ask whether the habituation theory—the idea that expressive writing causes people to habituate to negative thoughts and feelings—implies an answer. In this case, it seems clear that if the habituation theory is correct, then expressive writing about positive experiences should not be effective because it would not cause people to habituate to negative thoughts and feelings. A second way to derive hypotheses from theories is to focus on some component of the theory that has not yet been directly observed. For example, a researcher could focus on the process of habituation—perhaps hypothesizing that people should show fewer signs of emotional distress with each new writing session.

Among the very best hypotheses are those that distinguish between competing theories. For example, Norbert Schwarz and his colleagues considered two theories of how people make judgments about themselves, such as how assertive they are (Schwarz et al., 1991) [2] . Both theories held that such judgments are based on relevant examples that people bring to mind. However, one theory was that people base their judgments on the number of examples they bring to mind and the other was that people base their judgments on how easily they bring those examples to mind. To test these theories, the researchers asked people to recall either six times when they were assertive (which is easy for most people) or 12 times (which is difficult for most people). Then they asked them to judge their own assertiveness. Note that the number-of-examples theory implies that people who recalled 12 examples should judge themselves to be more assertive because they recalled more examples, but the ease-of-examples theory implies that participants who recalled six examples should judge themselves as more assertive because recalling the examples was easier. Thus the two theories made opposite predictions so that only one of the predictions could be confirmed. The surprising result was that participants who recalled fewer examples judged themselves to be more assertive—providing particularly convincing evidence in favor of the ease-of-retrieval theory over the number-of-examples theory.

Theory Testing

The primary way that scientific researchers use theories is sometimes called the hypothetico-deductive method (although this term is much more likely to be used by philosophers of science than by scientists themselves). Researchers begin with a set of phenomena and either construct a theory to explain or interpret them or choose an existing theory to work with. They then make a prediction about some new phenomenon that should be observed if the theory is correct. Again, this prediction is called a hypothesis. The researchers then conduct an empirical study to test the hypothesis. Finally, they reevaluate the theory in light of the new results and revise it if necessary. This process is usually conceptualized as a cycle because the researchers can then derive a new hypothesis from the revised theory, conduct a new empirical study to test the hypothesis, and so on. As Figure 2.3 shows, this approach meshes nicely with the model of scientific research in psychology presented earlier in the textbook—creating a more detailed model of “theoretically motivated” or “theory-driven” research.

As an example, let us consider Zajonc’s research on social facilitation and inhibition. He started with a somewhat contradictory pattern of results from the research literature. He then constructed his drive theory, according to which being watched by others while performing a task causes physiological arousal, which increases an organism’s tendency to make the dominant response. This theory predicts social facilitation for well-learned tasks and social inhibition for poorly learned tasks. He now had a theory that organized previous results in a meaningful way—but he still needed to test it. He hypothesized that if his theory was correct, he should observe that the presence of others improves performance in a simple laboratory task but inhibits performance in a difficult version of the very same laboratory task. To test this hypothesis, one of the studies he conducted used cockroaches as subjects (Zajonc, Heingartner, & Herman, 1969) [3] . The cockroaches ran either down a straight runway (an easy task for a cockroach) or through a cross-shaped maze (a difficult task for a cockroach) to escape into a dark chamber when a light was shined on them. They did this either while alone or in the presence of other cockroaches in clear plastic “audience boxes.” Zajonc found that cockroaches in the straight runway reached their goal more quickly in the presence of other cockroaches, but cockroaches in the cross-shaped maze reached their goal more slowly when they were in the presence of other cockroaches. Thus he confirmed his hypothesis and provided support for his drive theory. (Zajonc also showed that drive theory existed in humans [Zajonc & Sales, 1966] [4] in many other studies afterward).

Incorporating Theory into Your Research

When you write your research report or plan your presentation, be aware that there are two basic ways that researchers usually include theory. The first is to raise a research question, answer that question by conducting a new study, and then offer one or more theories (usually more) to explain or interpret the results. This format works well for applied research questions and for research questions that existing theories do not address. The second way is to describe one or more existing theories, derive a hypothesis from one of those theories, test the hypothesis in a new study, and finally reevaluate the theory. This format works well when there is an existing theory that addresses the research question—especially if the resulting hypothesis is surprising or conflicts with a hypothesis derived from a different theory.

To use theories in your research will not only give you guidance in coming up with experiment ideas and possible projects, but it lends legitimacy to your work. Psychologists have been interested in a variety of human behaviors and have developed many theories along the way. Using established theories will help you break new ground as a researcher, not limit you from developing your own ideas.

Characteristics of a Good Hypothesis

There are three general characteristics of a good hypothesis. First, a good hypothesis must be testable and falsifiable . We must be able to test the hypothesis using the methods of science and if you’ll recall Popper’s falsifiability criterion, it must be possible to gather evidence that will disconfirm the hypothesis if it is indeed false. Second, a good hypothesis must be logical. As described above, hypotheses are more than just a random guess. Hypotheses should be informed by previous theories or observations and logical reasoning. Typically, we begin with a broad and general theory and use deductive reasoning to generate a more specific hypothesis to test based on that theory. Occasionally, however, when there is no theory to inform our hypothesis, we use inductive reasoning which involves using specific observations or research findings to form a more general hypothesis. Finally, the hypothesis should be positive. That is, the hypothesis should make a positive statement about the existence of a relationship or effect, rather than a statement that a relationship or effect does not exist. As scientists, we don’t set out to show that relationships do not exist or that effects do not occur so our hypotheses should not be worded in a way to suggest that an effect or relationship does not exist. The nature of science is to assume that something does not exist and then seek to find evidence to prove this wrong, to show that it really does exist. That may seem backward to you but that is the nature of the scientific method. The underlying reason for this is beyond the scope of this chapter but it has to do with statistical theory.

Zajonc, R. B. (1965). Social facilitation. Science, 149 , 269–274 ↵
Schwarz, N., Bless, H., Strack, F., Klumpp, G., Rittenauer-Schatka, H., & Simons, A. (1991). Ease of retrieval as information: Another look at the availability heuristic. Journal of Personality and Social Psychology, 61 , 195–202. ↵
Zajonc, R. B., Heingartner, A., & Herman, E. M. (1969). Social enhancement and impairment of performance in the cockroach. Journal of Personality and Social Psychology, 13 , 83–92. ↵
Zajonc, R.B. & Sales, S.M. (1966). Social facilitation of dominant and subordinate responses. Journal of Experimental Social Psychology, 2 , 160-168. ↵

A coherent explanation or interpretation of one or more phenomena.

A specific prediction about a new phenomenon that should be observed if a particular theory is accurate.

A cyclical process of theory development, starting with an observed phenomenon, then developing or using a theory to make a specific prediction of what should happen if that theory is correct, testing that prediction, refining the theory in light of the findings, and using that refined theory to develop new hypotheses, and so on.

The ability to test the hypothesis using the methods of science and the possibility to gather evidence that will disconfirm the hypothesis if it is indeed false.

Developing a Hypothesis Copyright © 2022 by Rajiv S. Jhangiani; I-Chant A. Chiang; Carrie Cuttler; and Dana C. Leighton is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License , except where otherwise noted.

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Overview of the Scientific Method

10 Developing a Hypothesis

Learning objectives.

Distinguish between a theory and a hypothesis.
Discover how theories are used to generate hypotheses and how the results of studies can be used to further inform theories.
Understand the characteristics of a good hypothesis.

Theories and Hypotheses

Theory Testing

Incorporating Theory into Your Research

Characteristics of a Good Hypothesis

Zajonc, R. B. (1965). Social facilitation. Science, 149 , 269–274 ↵
Schwarz, N., Bless, H., Strack, F., Klumpp, G., Rittenauer-Schatka, H., & Simons, A. (1991). Ease of retrieval as information: Another look at the availability heuristic. Journal of Personality and Social Psychology, 61 , 195–202. ↵
Zajonc, R. B., Heingartner, A., & Herman, E. M. (1969). Social enhancement and impairment of performance in the cockroach. Journal of Personality and Social Psychology, 13 , 83–92. ↵
Zajonc, R.B. & Sales, S.M. (1966). Social facilitation of dominant and subordinate responses. Journal of Experimental Social Psychology, 2 , 160-168. ↵

A coherent explanation or interpretation of one or more phenomena.

A specific prediction about a new phenomenon that should be observed if a particular theory is accurate.

The ability to test the hypothesis using the methods of science and the possibility to gather evidence that will disconfirm the hypothesis if it is indeed false.

Research Methods in Psychology Copyright © 2019 by Rajiv S. Jhangiani, I-Chant A. Chiang, Carrie Cuttler, & Dana C. Leighton is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License , except where otherwise noted.

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Research Hypothesis In Psychology: Types, & Examples

Saul Mcleod, PhD

Editor-in-Chief for Simply Psychology

BSc (Hons) Psychology, MRes, PhD, University of Manchester

Saul Mcleod, PhD., is a qualified psychology teacher with over 18 years of experience in further and higher education. He has been published in peer-reviewed journals, including the Journal of Clinical Psychology.

Learn about our Editorial Process

Olivia Guy-Evans, MSc

Associate Editor for Simply Psychology

BSc (Hons) Psychology, MSc Psychology of Education

Olivia Guy-Evans is a writer and associate editor for Simply Psychology. She has previously worked in healthcare and educational sectors.

On This Page:

A research hypothesis, in its plural form “hypotheses,” is a specific, testable prediction about the anticipated results of a study, established at its outset. It is a key component of the scientific method .

Hypotheses connect theory to data and guide the research process towards expanding scientific understanding

Some key points about hypotheses:

A hypothesis expresses an expected pattern or relationship. It connects the variables under investigation.
It is stated in clear, precise terms before any data collection or analysis occurs. This makes the hypothesis testable.
A hypothesis must be falsifiable. It should be possible, even if unlikely in practice, to collect data that disconfirms rather than supports the hypothesis.
Hypotheses guide research. Scientists design studies to explicitly evaluate hypotheses about how nature works.
For a hypothesis to be valid, it must be testable against empirical evidence. The evidence can then confirm or disprove the testable predictions.
Hypotheses are informed by background knowledge and observation, but go beyond what is already known to propose an explanation of how or why something occurs.

Predictions typically arise from a thorough knowledge of the research literature, curiosity about real-world problems or implications, and integrating this to advance theory. They build on existing literature while providing new insight.

Types of Research Hypotheses

Alternative hypothesis.

The research hypothesis is often called the alternative or experimental hypothesis in experimental research.

It typically suggests a potential relationship between two key variables: the independent variable, which the researcher manipulates, and the dependent variable, which is measured based on those changes.

The alternative hypothesis states a relationship exists between the two variables being studied (one variable affects the other).

A hypothesis is a testable statement or prediction about the relationship between two or more variables. It is a key component of the scientific method. Some key points about hypotheses:

Important hypotheses lead to predictions that can be tested empirically. The evidence can then confirm or disprove the testable predictions.

In summary, a hypothesis is a precise, testable statement of what researchers expect to happen in a study and why. Hypotheses connect theory to data and guide the research process towards expanding scientific understanding.

An experimental hypothesis predicts what change(s) will occur in the dependent variable when the independent variable is manipulated.

It states that the results are not due to chance and are significant in supporting the theory being investigated.

The alternative hypothesis can be directional, indicating a specific direction of the effect, or non-directional, suggesting a difference without specifying its nature. It’s what researchers aim to support or demonstrate through their study.

Null Hypothesis

The null hypothesis states no relationship exists between the two variables being studied (one variable does not affect the other). There will be no changes in the dependent variable due to manipulating the independent variable.

It states results are due to chance and are not significant in supporting the idea being investigated.

The null hypothesis, positing no effect or relationship, is a foundational contrast to the research hypothesis in scientific inquiry. It establishes a baseline for statistical testing, promoting objectivity by initiating research from a neutral stance.

Many statistical methods are tailored to test the null hypothesis, determining the likelihood of observed results if no true effect exists.

This dual-hypothesis approach provides clarity, ensuring that research intentions are explicit, and fosters consistency across scientific studies, enhancing the standardization and interpretability of research outcomes.

Nondirectional Hypothesis

A non-directional hypothesis, also known as a two-tailed hypothesis, predicts that there is a difference or relationship between two variables but does not specify the direction of this relationship.

It merely indicates that a change or effect will occur without predicting which group will have higher or lower values.

For example, “There is a difference in performance between Group A and Group B” is a non-directional hypothesis.

Directional Hypothesis

A directional (one-tailed) hypothesis predicts the nature of the effect of the independent variable on the dependent variable. It predicts in which direction the change will take place. (i.e., greater, smaller, less, more)

It specifies whether one variable is greater, lesser, or different from another, rather than just indicating that there’s a difference without specifying its nature.

For example, “Exercise increases weight loss” is a directional hypothesis.

Falsifiability

The Falsification Principle, proposed by Karl Popper , is a way of demarcating science from non-science. It suggests that for a theory or hypothesis to be considered scientific, it must be testable and irrefutable.

Falsifiability emphasizes that scientific claims shouldn’t just be confirmable but should also have the potential to be proven wrong.

It means that there should exist some potential evidence or experiment that could prove the proposition false.

However many confirming instances exist for a theory, it only takes one counter observation to falsify it. For example, the hypothesis that “all swans are white,” can be falsified by observing a black swan.

For Popper, science should attempt to disprove a theory rather than attempt to continually provide evidence to support a research hypothesis.

Can a Hypothesis be Proven?

Hypotheses make probabilistic predictions. They state the expected outcome if a particular relationship exists. However, a study result supporting a hypothesis does not definitively prove it is true.

All studies have limitations. There may be unknown confounding factors or issues that limit the certainty of conclusions. Additional studies may yield different results.

In science, hypotheses can realistically only be supported with some degree of confidence, not proven. The process of science is to incrementally accumulate evidence for and against hypothesized relationships in an ongoing pursuit of better models and explanations that best fit the empirical data. But hypotheses remain open to revision and rejection if that is where the evidence leads.

Disproving a hypothesis is definitive. Solid disconfirmatory evidence will falsify a hypothesis and require altering or discarding it based on the evidence.
However, confirming evidence is always open to revision. Other explanations may account for the same results, and additional or contradictory evidence may emerge over time.

We can never 100% prove the alternative hypothesis. Instead, we see if we can disprove, or reject the null hypothesis.

If we reject the null hypothesis, this doesn’t mean that our alternative hypothesis is correct but does support the alternative/experimental hypothesis.

Upon analysis of the results, an alternative hypothesis can be rejected or supported, but it can never be proven to be correct. We must avoid any reference to results proving a theory as this implies 100% certainty, and there is always a chance that evidence may exist which could refute a theory.

How to Write a Hypothesis

Identify variables . The researcher manipulates the independent variable and the dependent variable is the measured outcome.
Operationalized the variables being investigated . Operationalization of a hypothesis refers to the process of making the variables physically measurable or testable, e.g. if you are about to study aggression, you might count the number of punches given by participants.
Decide on a direction for your prediction . If there is evidence in the literature to support a specific effect of the independent variable on the dependent variable, write a directional (one-tailed) hypothesis. If there are limited or ambiguous findings in the literature regarding the effect of the independent variable on the dependent variable, write a non-directional (two-tailed) hypothesis.
Make it Testable : Ensure your hypothesis can be tested through experimentation or observation. It should be possible to prove it false (principle of falsifiability).
Clear & concise language . A strong hypothesis is concise (typically one to two sentences long), and formulated using clear and straightforward language, ensuring it’s easily understood and testable.

Consider a hypothesis many teachers might subscribe to: students work better on Monday morning than on Friday afternoon (IV=Day, DV= Standard of work).

Now, if we decide to study this by giving the same group of students a lesson on a Monday morning and a Friday afternoon and then measuring their immediate recall of the material covered in each session, we would end up with the following:

The alternative hypothesis states that students will recall significantly more information on a Monday morning than on a Friday afternoon.
The null hypothesis states that there will be no significant difference in the amount recalled on a Monday morning compared to a Friday afternoon. Any difference will be due to chance or confounding factors.

More Examples

Memory : Participants exposed to classical music during study sessions will recall more items from a list than those who studied in silence.
Social Psychology : Individuals who frequently engage in social media use will report higher levels of perceived social isolation compared to those who use it infrequently.
Developmental Psychology : Children who engage in regular imaginative play have better problem-solving skills than those who don’t.
Clinical Psychology : Cognitive-behavioral therapy will be more effective in reducing symptoms of anxiety over a 6-month period compared to traditional talk therapy.
Cognitive Psychology : Individuals who multitask between various electronic devices will have shorter attention spans on focused tasks than those who single-task.
Health Psychology : Patients who practice mindfulness meditation will experience lower levels of chronic pain compared to those who don’t meditate.
Organizational Psychology : Employees in open-plan offices will report higher levels of stress than those in private offices.
Behavioral Psychology : Rats rewarded with food after pressing a lever will press it more frequently than rats who receive no reward.

Hypothesis vs. Theory: A Simple Guide to Tell Them Apart

By: Author ESLBUZZ

Posted on Last updated: July 27, 2023

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Hypothesis and theory are no stranger to those who conduct studies and work in science. These two terms are often used interchangeably by non-researchers, but they have distinct meanings in the scientific community. Understanding the difference between a hypothesis and a theory is essential for anyone interested in scientific research or critical thinking.

In this article, we will explore the differences between hypothesis and theory and provide examples to help you understand how they are used in scientific research. We will also discuss the importance of these terms in the scientific method and how they contribute to our understanding of the natural world. Whether you are a student, a researcher, or simply someone interested in science, this article will provide valuable insights into the world of scientific research.

To help illustrate the differences between hypothesis and theory, we will provide a comparison table that summarizes the key differences between these two terms and examples of how scientists use hypotheses and theories to explain natural phenomena and make predictions about future events. By the end of this article, you will have a clear understanding of the differences between hypothesis and theory and how they are used in scientific research.

Hypothesis vs. Theory

Hypothesis vs. Theory: Definitions

Understanding hypothesis.

A hypothesis is an educated guess or assumption that is made before conducting research. It is a tentative explanation for a phenomenon or observation that is based on limited evidence or prior knowledge. In other words, a hypothesis is a statement that proposes a relationship between two or more variables, which can be tested through further investigation.

Characteristics of Hypothesis

Hypotheses have certain characteristics that set them apart from other types of statements. These characteristics include:

Testable: A hypothesis must be testable through empirical research. This means that it must be possible to collect data that can either support or refute the hypothesis.
Specific: A hypothesis must be specific in its predictions. It should clearly state what is expected to happen and under what conditions.
Falsifiable: A hypothesis must be falsifiable, which means that it must be possible to disprove the hypothesis if it is not supported by the evidence.
Parsimonious: A hypothesis should be simple and straightforward. It should not include unnecessary assumptions or variables.

Examples of Hypothesis

Here are some examples of hypotheses:

If a plant is exposed to sunlight, then it will grow faster than a plant that is not exposed to sunlight.
If a person consumes more calories than they burn, then they will gain weight.
If students are given more time to study for an exam, then they will perform better on the exam.

In summary, a hypothesis is an educated guess or assumption that is made before conducting research. It is testable, specific, falsifiable, and parsimonious. Examples of hypotheses include statements that propose a relationship between two or more variables, which can be tested through further investigation.

Understanding Theory

Definition of Theory

In scientific terms, a theory is a well-substantiated explanation of some aspect of the natural world that is based on empirical evidence. It is a collection of ideas that have been tested and confirmed through observation and experimentation. A theory is a framework that explains how and why things work in a certain way. It is a set of principles that can be used to make predictions about future events.

Characteristics of Theory

A theory has several characteristics that distinguish it from other scientific concepts such as hypotheses or laws. Some of the key characteristics of a theory are:

A theory is based on empirical evidence and is supported by multiple lines of evidence.
A theory is constantly evolving and can be modified or refined as new evidence emerges.
A theory is generally accepted as true by the scientific community and is widely used to make predictions and guide research.
A theory is not a guess or a hunch, but a well-substantiated explanation that has been rigorously tested.

Examples of Theory

There are many examples of well-established theories in science. Here are a few examples:

In summary, a theory is a well-substantiated explanation of some aspect of the natural world that is based on empirical evidence. It is a framework that explains how and why things work in a certain way and is constantly evolving as new evidence emerges. Theories are widely accepted as true by the scientific community and are used to make predictions and guide research.

Hypothesis vs. Theory: The Distinctions

As a writer, it is important to understand the differences between a hypothesis and a theory. These two scientific terms are often used interchangeably, but they have drastically different meanings in the world of science. In this section, we will explore the process of formulation, level of proof, and usage in the scientific community.

Process of Formulation

A hypothesis is an educated guess or assumption made before any research has been done. It is formed so that it can be tested to see if it might be true. Hypotheses are often based on observations or previous research and can be either proven or disproven through experimentation.

On the other hand, a theory is a well-established principle that is formed to explain the things already shown in data. Theories are based on a large body of evidence and have been extensively tested and proven through experimentation. The formulation of a theory requires a lot of research, experimentation, and analysis.

Level of Proof

The level of proof required for a hypothesis and a theory is vastly different. A hypothesis requires a certain level of proof to be considered valid, but it can still be disproven through experimentation. In contrast, a theory has been extensively tested and proven through experimentation, and therefore requires a much higher level of proof to be disproven.

Usage in Scientific Community

In the scientific community, hypotheses and theories play different roles. Hypotheses are used to generate predictions and testable explanations for phenomena, while theories are used to explain and predict a wide range of phenomena. Hypotheses are usually the starting point for research, while theories are the end result of extensive research and experimentation.

To summarize, a hypothesis is an educated guess or assumption made before any research has been done, while a theory is a well-established principle that is formed to explain the things already shown in data. Hypotheses require a certain level of proof to be considered valid, while theories require a much higher level of proof. In the scientific community, hypotheses are used to generate predictions and testable explanations for phenomena, while theories are used to explain and predict a wide range of phenomena.

Hypothesis vs. Theory: Common Misconceptions

When it comes to scientific research, there are several misconceptions about the differences between hypothesis and theory. In this section, we’ll explore some of the most common misconceptions and clarify the differences between these two scientific terms.

Misconception #1: Hypotheses are less important than theories

One common misconception is that hypotheses are less important than theories. This is not true. A hypothesis is the foundation of scientific research, as it is a proposed explanation for an observation or phenomenon. Without a hypothesis, there can be no scientific investigation.

Misconception #2: Hypotheses are guesses

Another common misconception is that hypotheses are guesses. While a hypothesis is an educated guess, it is not a random or arbitrary guess. A hypothesis is based on prior knowledge, observations, and data. It is a proposed explanation that can be tested through experimentation.

Misconception #3: Theories are proven facts

Many people believe that theories are proven facts. This is not true. A theory is a well-substantiated explanation for a set of observations or phenomena. It is based on a large body of evidence and has been repeatedly tested and confirmed through experimentation. However, theories are not absolute truths and are subject to revision or rejection based on new evidence.

Misconception #4: Hypotheses become theories

Some people believe that hypotheses become theories once they are proven. This is not true. A hypothesis can be supported or rejected by experimental evidence, but it does not become a theory. A theory is a broader explanation that encompasses many hypotheses and has been extensively tested and confirmed.

Misconception #5: Theories are more certain than hypotheses

Another common misconception is that theories are more certain than hypotheses. While theories are based on a large body of evidence and have been extensively tested, they are not absolute truths. Theories are subject to revision or rejection based on new evidence, just like hypotheses.

In summary, hypotheses and theories are both important components of scientific research. Hypotheses are proposed explanations that can be tested through experimentation, while theories are well-substantiated explanations that have been extensively tested and confirmed. While there are many misconceptions about the differences between hypotheses vs. theory, understanding these differences is crucial for conducting scientific research.

In conclusion, while the terms “hypothesis” and “theory” are often used interchangeably, they have distinct differences in the scientific method. A hypothesis is an assumption made before any research has been done, formed so that it can be tested to see if it might be true. On the other hand, a theory is a principle formed to explain the things already shown in data.

One way to differentiate between a hypothesis and a theory is to consider the level of evidence supporting each. A hypothesis is a proposed explanation for a phenomenon, but it is not yet supported by sufficient evidence. In contrast, a theory is a well-established explanation for a phenomenon that has been supported by a large body of evidence.

Another way to differentiate between a hypothesis and a theory is to consider their role in the scientific method. A hypothesis is an initial step in the scientific method, where a researcher formulates a testable prediction about a phenomenon. A theory, on the other hand, is the end result of the scientific method, where a researcher has tested and confirmed a hypothesis over time.

It is important to note that a hypothesis can eventually become a theory if it is repeatedly tested and supported by evidence. However, a theory can never become a hypothesis, as it is already a well-established explanation for a phenomenon.

In summary, understanding the differences between hypothesis and theory is crucial for conducting and interpreting scientific research. By using these terms correctly, researchers can communicate their ideas clearly and accurately, contributing to the advancement of scientific knowledge.

Frequently Asked Questions

How can you distinguish between hypothesis and theory?

A hypothesis is an educated guess or a proposed explanation for an observation or phenomenon. It is a tentative explanation that can be tested through experiments and observations. On the other hand, a theory is a well-established explanation that has been supported by a large body of evidence. The main difference between a hypothesis and a theory is that a hypothesis is a proposed explanation that needs to be tested, while a theory is a well-supported explanation that has been tested and confirmed by multiple lines of evidence.

What is the difference between a theory and a hypothesis in biology?

In biology, a hypothesis is a proposed explanation for a biological phenomenon that can be tested through experiments and observations. For example, a biologist might propose a hypothesis to explain why a particular species of bird has a particular beak shape. A theory in biology, on the other hand, is a well-established explanation that has been supported by a large body of evidence. For example, the theory of evolution is a well-established explanation for the diversity of life on Earth.

What is an example of a theory statement?

A theory statement is a statement that summarizes a well-established explanation for a phenomenon. For example, the theory of relativity is a statement that summarizes Einstein’s well-established explanation for the behavior of objects in space and time.

How are hypotheses and theories similar and different?

Both hypotheses and theories are proposed explanations for phenomena. However, while hypotheses are tentative and need to be tested, theories are well-established and have been supported by a large body of evidence. In addition, hypotheses are often specific to a particular observation or phenomenon, while theories are more general and can explain a wide range of phenomena.

What are some examples of the differences between a hypothesis and a theory?

An example of a hypothesis might be that a particular drug will cure a particular disease. An example of a theory might be the theory of plate tectonics, which explains the movement of the Earth’s crust. The main difference between these two examples is that the first is a tentative explanation that needs to be tested, while the second is a well-established explanation that has been supported by a large body of evidence.

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A theory statement is a statement that summarizes a well-established explanation for a phenomenon. For example, the theory of relativity is a statement that summarizes Einstein's well-established explanation for the behavior of objects in space and time.

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The best way to distinguish between hypotheses and theories is to remember that hypotheses are tentative explanations that need to be tested, while theories are well-established explanations that have been supported by a large body of evidence.

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An example of a hypothesis might be that a particular drug will cure a particular disease. An example of a theory might be the theory of plate tectonics, which explains the movement of the Earth's crust. The main difference between these two examples is that the first is a tentative explanation that needs to be tested, while the second is a well-established explanation that has been supported by a large body of evidence.

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Hypothesis Testing | A Step-by-Step Guide with Easy Examples

Published on November 8, 2019 by Rebecca Bevans . Revised on June 22, 2023.

Hypothesis testing is a formal procedure for investigating our ideas about the world using statistics . It is most often used by scientists to test specific predictions, called hypotheses, that arise from theories.

There are 5 main steps in hypothesis testing:

State your research hypothesis as a null hypothesis and alternate hypothesis (H o ) and (H a or H 1 ).
Collect data in a way designed to test the hypothesis.
Perform an appropriate statistical test .
Decide whether to reject or fail to reject your null hypothesis.
Present the findings in your results and discussion section.

Though the specific details might vary, the procedure you will use when testing a hypothesis will always follow some version of these steps.

Step 1: state your null and alternate hypothesis, step 2: collect data, step 3: perform a statistical test, step 4: decide whether to reject or fail to reject your null hypothesis, step 5: present your findings, other interesting articles, frequently asked questions about hypothesis testing.

After developing your initial research hypothesis (the prediction that you want to investigate), it is important to restate it as a null (H o ) and alternate (H a ) hypothesis so that you can test it mathematically.

The alternate hypothesis is usually your initial hypothesis that predicts a relationship between variables. The null hypothesis is a prediction of no relationship between the variables you are interested in.

H 0 : Men are, on average, not taller than women. H a : Men are, on average, taller than women.

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For a statistical test to be valid , it is important to perform sampling and collect data in a way that is designed to test your hypothesis. If your data are not representative, then you cannot make statistical inferences about the population you are interested in.

There are a variety of statistical tests available, but they are all based on the comparison of within-group variance (how spread out the data is within a category) versus between-group variance (how different the categories are from one another).

If the between-group variance is large enough that there is little or no overlap between groups, then your statistical test will reflect that by showing a low p -value . This means it is unlikely that the differences between these groups came about by chance.

Alternatively, if there is high within-group variance and low between-group variance, then your statistical test will reflect that with a high p -value. This means it is likely that any difference you measure between groups is due to chance.

Your choice of statistical test will be based on the type of variables and the level of measurement of your collected data .

an estimate of the difference in average height between the two groups.
a p -value showing how likely you are to see this difference if the null hypothesis of no difference is true.

Based on the outcome of your statistical test, you will have to decide whether to reject or fail to reject your null hypothesis.

In most cases you will use the p -value generated by your statistical test to guide your decision. And in most cases, your predetermined level of significance for rejecting the null hypothesis will be 0.05 – that is, when there is a less than 5% chance that you would see these results if the null hypothesis were true.

In some cases, researchers choose a more conservative level of significance, such as 0.01 (1%). This minimizes the risk of incorrectly rejecting the null hypothesis ( Type I error ).

The results of hypothesis testing will be presented in the results and discussion sections of your research paper , dissertation or thesis .

In the results section you should give a brief summary of the data and a summary of the results of your statistical test (for example, the estimated difference between group means and associated p -value). In the discussion , you can discuss whether your initial hypothesis was supported by your results or not.

In the formal language of hypothesis testing, we talk about rejecting or failing to reject the null hypothesis. You will probably be asked to do this in your statistics assignments.

However, when presenting research results in academic papers we rarely talk this way. Instead, we go back to our alternate hypothesis (in this case, the hypothesis that men are on average taller than women) and state whether the result of our test did or did not support the alternate hypothesis.

If your null hypothesis was rejected, this result is interpreted as “supported the alternate hypothesis.”

These are superficial differences; you can see that they mean the same thing.

You might notice that we don’t say that we reject or fail to reject the alternate hypothesis . This is because hypothesis testing is not designed to prove or disprove anything. It is only designed to test whether a pattern we measure could have arisen spuriously, or by chance.

If we reject the null hypothesis based on our research (i.e., we find that it is unlikely that the pattern arose by chance), then we can say our test lends support to our hypothesis . But if the pattern does not pass our decision rule, meaning that it could have arisen by chance, then we say the test is inconsistent with our hypothesis .

If you want to know more about statistics , methodology , or research bias , make sure to check out some of our other articles with explanations and examples.

Normal distribution
Descriptive statistics
Measures of central tendency
Correlation coefficient

Methodology

Cluster sampling
Stratified sampling
Types of interviews
Cohort study
Thematic analysis

Research bias

Implicit bias
Cognitive bias
Survivorship bias
Availability heuristic
Nonresponse bias
Regression to the mean

Hypothesis testing is a formal procedure for investigating our ideas about the world using statistics. It is used by scientists to test specific predictions, called hypotheses , by calculating how likely it is that a pattern or relationship between variables could have arisen by chance.

A hypothesis states your predictions about what your research will find. It is a tentative answer to your research question that has not yet been tested. For some research projects, you might have to write several hypotheses that address different aspects of your research question.

A hypothesis is not just a guess — it should be based on existing theories and knowledge. It also has to be testable, which means you can support or refute it through scientific research methods (such as experiments, observations and statistical analysis of data).

Null and alternative hypotheses are used in statistical hypothesis testing . The null hypothesis of a test always predicts no effect or no relationship between variables, while the alternative hypothesis states your research prediction of an effect or relationship.

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Difference Between Hypothesis And Theory

Difference Between Theory and Hypothesis

Many of them belittle evolution because “it is just a theory.” Gravity, on the other hand, must be real because it is a law. The words “theory,” “facts,” “laws” and “hypothesis” have a very specific meaning in the scientific world that doesn’t quite match the ones we use in everyday language. A hypothesis is a tentative explanation of an observation that can be tested. It acts as a starting point for further explanation. Theory, on the other hand, is an explanation of some aspect of the natural world that’s well-justified by facts, tested hypotheses, and laws. Let us look at more differences between hypothesis and theory given in a tabular column below.

Theory vs Hypothesis

From the above differences, we can infer that a hypothesis might change significantly as the testing occurs. A hypothesis can either be right or wrong. When a hypothesis is tested and proved true, it becomes a theory. At BYJU’S, learn more differences like the difference between asteroid and comet.

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How to Write a Great Hypothesis

Hypothesis Format, Examples, and Tips

Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book."

Amy Morin, LCSW, is a psychotherapist and international bestselling author. Her books, including "13 Things Mentally Strong People Don't Do," have been translated into more than 40 languages. Her TEDx talk, "The Secret of Becoming Mentally Strong," is one of the most viewed talks of all time.

Verywell / Alex Dos Diaz

The Scientific Method

Hypothesis Format

Falsifiability of a hypothesis, operational definitions, types of hypotheses, hypotheses examples.

Collecting Data

Frequently Asked Questions

A hypothesis is a tentative statement about the relationship between two or more variables. It is a specific, testable prediction about what you expect to happen in a study.

One hypothesis example would be a study designed to look at the relationship between sleep deprivation and test performance might have a hypothesis that states: "This study is designed to assess the hypothesis that sleep-deprived people will perform worse on a test than individuals who are not sleep-deprived."

This article explores how a hypothesis is used in psychology research, how to write a good hypothesis, and the different types of hypotheses you might use.

The Hypothesis in the Scientific Method

In the scientific method , whether it involves research in psychology, biology, or some other area, a hypothesis represents what the researchers think will happen in an experiment. The scientific method involves the following steps:

Forming a question
Performing background research
Creating a hypothesis
Designing an experiment
Collecting data
Analyzing the results
Drawing conclusions
Communicating the results

The hypothesis is a prediction, but it involves more than a guess. Most of the time, the hypothesis begins with a question which is then explored through background research. It is only at this point that researchers begin to develop a testable hypothesis. Unless you are creating an exploratory study, your hypothesis should always explain what you expect to happen.

In a study exploring the effects of a particular drug, the hypothesis might be that researchers expect the drug to have some type of effect on the symptoms of a specific illness. In psychology, the hypothesis might focus on how a certain aspect of the environment might influence a particular behavior.

Remember, a hypothesis does not have to be correct. While the hypothesis predicts what the researchers expect to see, the goal of the research is to determine whether this guess is right or wrong. When conducting an experiment, researchers might explore a number of factors to determine which ones might contribute to the ultimate outcome.

In many cases, researchers may find that the results of an experiment do not support the original hypothesis. When writing up these results, the researchers might suggest other options that should be explored in future studies.

In many cases, researchers might draw a hypothesis from a specific theory or build on previous research. For example, prior research has shown that stress can impact the immune system. So a researcher might hypothesize: "People with high-stress levels will be more likely to contract a common cold after being exposed to the virus than people who have low-stress levels."

In other instances, researchers might look at commonly held beliefs or folk wisdom. "Birds of a feather flock together" is one example of folk wisdom that a psychologist might try to investigate. The researcher might pose a specific hypothesis that "People tend to select romantic partners who are similar to them in interests and educational level."

Elements of a Good Hypothesis

So how do you write a good hypothesis? When trying to come up with a hypothesis for your research or experiments, ask yourself the following questions:

Is your hypothesis based on your research on a topic?
Can your hypothesis be tested?
Does your hypothesis include independent and dependent variables?

Before you come up with a specific hypothesis, spend some time doing background research. Once you have completed a literature review, start thinking about potential questions you still have. Pay attention to the discussion section in the journal articles you read . Many authors will suggest questions that still need to be explored.

To form a hypothesis, you should take these steps:

Collect as many observations about a topic or problem as you can.
Evaluate these observations and look for possible causes of the problem.
Create a list of possible explanations that you might want to explore.
After you have developed some possible hypotheses, think of ways that you could confirm or disprove each hypothesis through experimentation. This is known as falsifiability.

In the scientific method , falsifiability is an important part of any valid hypothesis. In order to test a claim scientifically, it must be possible that the claim could be proven false.

Students sometimes confuse the idea of falsifiability with the idea that it means that something is false, which is not the case. What falsifiability means is that if something was false, then it is possible to demonstrate that it is false.

One of the hallmarks of pseudoscience is that it makes claims that cannot be refuted or proven false.

A variable is a factor or element that can be changed and manipulated in ways that are observable and measurable. However, the researcher must also define how the variable will be manipulated and measured in the study.

For example, a researcher might operationally define the variable " test anxiety " as the results of a self-report measure of anxiety experienced during an exam. A "study habits" variable might be defined by the amount of studying that actually occurs as measured by time.

These precise descriptions are important because many things can be measured in a number of different ways. One of the basic principles of any type of scientific research is that the results must be replicable. By clearly detailing the specifics of how the variables were measured and manipulated, other researchers can better understand the results and repeat the study if needed.

Some variables are more difficult than others to define. How would you operationally define a variable such as aggression ? For obvious ethical reasons, researchers cannot create a situation in which a person behaves aggressively toward others.

In order to measure this variable, the researcher must devise a measurement that assesses aggressive behavior without harming other people. In this situation, the researcher might utilize a simulated task to measure aggressiveness.

Hypothesis Checklist

Does your hypothesis focus on something that you can actually test?
Does your hypothesis include both an independent and dependent variable?
Can you manipulate the variables?
Can your hypothesis be tested without violating ethical standards?

The hypothesis you use will depend on what you are investigating and hoping to find. Some of the main types of hypotheses that you might use include:

Simple hypothesis : This type of hypothesis suggests that there is a relationship between one independent variable and one dependent variable.
Complex hypothesis : This type of hypothesis suggests a relationship between three or more variables, such as two independent variables and a dependent variable.
Null hypothesis : This hypothesis suggests no relationship exists between two or more variables.
Alternative hypothesis : This hypothesis states the opposite of the null hypothesis.
Statistical hypothesis : This hypothesis uses statistical analysis to evaluate a representative sample of the population and then generalizes the findings to the larger group.
Logical hypothesis : This hypothesis assumes a relationship between variables without collecting data or evidence.

A hypothesis often follows a basic format of "If {this happens} then {this will happen}." One way to structure your hypothesis is to describe what will happen to the dependent variable if you change the independent variable .

The basic format might be: "If {these changes are made to a certain independent variable}, then we will observe {a change in a specific dependent variable}."

A few examples of simple hypotheses:

"Students who eat breakfast will perform better on a math exam than students who do not eat breakfast."
Complex hypothesis: "Students who experience test anxiety before an English exam will get lower scores than students who do not experience test anxiety."
"Motorists who talk on the phone while driving will be more likely to make errors on a driving course than those who do not talk on the phone."

Examples of a complex hypothesis include:

"People with high-sugar diets and sedentary activity levels are more likely to develop depression."
"Younger people who are regularly exposed to green, outdoor areas have better subjective well-being than older adults who have limited exposure to green spaces."

Examples of a null hypothesis include:

"Children who receive a new reading intervention will have scores different than students who do not receive the intervention."
"There will be no difference in scores on a memory recall task between children and adults."

Examples of an alternative hypothesis:

"Children who receive a new reading intervention will perform better than students who did not receive the intervention."
"Adults will perform better on a memory task than children."

Collecting Data on Your Hypothesis

Once a researcher has formed a testable hypothesis, the next step is to select a research design and start collecting data. The research method depends largely on exactly what they are studying. There are two basic types of research methods: descriptive research and experimental research.

Descriptive Research Methods

Descriptive research such as case studies , naturalistic observations , and surveys are often used when it would be impossible or difficult to conduct an experiment . These methods are best used to describe different aspects of a behavior or psychological phenomenon.

Once a researcher has collected data using descriptive methods, a correlational study can then be used to look at how the variables are related. This type of research method might be used to investigate a hypothesis that is difficult to test experimentally.

Experimental Research Methods

Experimental methods are used to demonstrate causal relationships between variables. In an experiment, the researcher systematically manipulates a variable of interest (known as the independent variable) and measures the effect on another variable (known as the dependent variable).

Unlike correlational studies, which can only be used to determine if there is a relationship between two variables, experimental methods can be used to determine the actual nature of the relationship—whether changes in one variable actually cause another to change.

A Word From Verywell

The hypothesis is a critical part of any scientific exploration. It represents what researchers expect to find in a study or experiment. In situations where the hypothesis is unsupported by the research, the research still has value. Such research helps us better understand how different aspects of the natural world relate to one another. It also helps us develop new hypotheses that can then be tested in the future.

Some examples of how to write a hypothesis include:

"Staying up late will lead to worse test performance the next day."
"People who consume one apple each day will visit the doctor fewer times each year."
"Breaking study sessions up into three 20-minute sessions will lead to better test results than a single 60-minute study session."

The four parts of a hypothesis are:

The research question
The independent variable (IV)
The dependent variable (DV)
The proposed relationship between the IV and DV

Castillo M. The scientific method: a need for something better? . AJNR Am J Neuroradiol. 2013;34(9):1669-71. doi:10.3174/ajnr.A3401

Nevid J. Psychology: Concepts and Applications. Wadworth, 2013.

By Kendra Cherry, MSEd Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book."

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Definition of theory

Did you know.

The Difference Between Hypothesis and Theory

A hypothesis is an assumption, an idea that is proposed for the sake of argument so that it can be tested to see if it might be true.

In the scientific method, the hypothesis is constructed before any applicable research has been done, apart from a basic background review. You ask a question, read up on what has been studied before, and then form a hypothesis.

A hypothesis is usually tentative; it's an assumption or suggestion made strictly for the objective of being tested.

A theory , in contrast, is a principle that has been formed as an attempt to explain things that have already been substantiated by data. It is used in the names of a number of principles accepted in the scientific community, such as the Big Bang Theory . Because of the rigors of experimentation and control, it is understood to be more likely to be true than a hypothesis is.

In non-scientific use, however, hypothesis and theory are often used interchangeably to mean simply an idea, speculation, or hunch, with theory being the more common choice.

Since this casual use does away with the distinctions upheld by the scientific community, hypothesis and theory are prone to being wrongly interpreted even when they are encountered in scientific contexts—or at least, contexts that allude to scientific study without making the critical distinction that scientists employ when weighing hypotheses and theories.

The most common occurrence is when theory is interpreted—and sometimes even gleefully seized upon—to mean something having less truth value than other scientific principles. (The word law applies to principles so firmly established that they are almost never questioned, such as the law of gravity.)

This mistake is one of projection: since we use theory in general to mean something lightly speculated, then it's implied that scientists must be talking about the same level of uncertainty when they use theory to refer to their well-tested and reasoned principles.

The distinction has come to the forefront particularly on occasions when the content of science curricula in schools has been challenged—notably, when a school board in Georgia put stickers on textbooks stating that evolution was "a theory, not a fact, regarding the origin of living things." As Kenneth R. Miller, a cell biologist at Brown University, has said , a theory "doesn’t mean a hunch or a guess. A theory is a system of explanations that ties together a whole bunch of facts. It not only explains those facts, but predicts what you ought to find from other observations and experiments.”

While theories are never completely infallible, they form the basis of scientific reasoning because, as Miller said "to the best of our ability, we’ve tested them, and they’ve held up."

Two Related, Yet Distinct, Meanings of Theory

There are many shades of meaning to the word theory . Most of these are used without difficulty, and we understand, based on the context in which they are found, what the intended meaning is. For instance, when we speak of music theory we understand it to be in reference to the underlying principles of the composition of music, and not in reference to some speculation about those principles.

However, there are two senses of theory which are sometimes troublesome. These are the senses which are defined as “a plausible or scientifically acceptable general principle or body of principles offered to explain phenomena” and “an unproven assumption; conjecture.” The second of these is occasionally misapplied in cases where the former is meant, as when a particular scientific theory is derided as "just a theory," implying that it is no more than speculation or conjecture . One may certainly disagree with scientists regarding their theories, but it is an inaccurate interpretation of language to regard their use of the word as implying a tentative hypothesis; the scientific use of theory is quite different than the speculative use of the word.

proposition
supposition

hypothesis , theory , law mean a formula derived by inference from scientific data that explains a principle operating in nature.

hypothesis implies insufficient evidence to provide more than a tentative explanation.

theory implies a greater range of evidence and greater likelihood of truth.

law implies a statement of order and relation in nature that has been found to be invariable under the same conditions.

Examples of theory in a Sentence

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'theory.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

Late Latin theoria , from Greek theōria , from theōrein

1592, in the meaning defined at sense 6

Phrases Containing theory

atomic theory
Bohr theory
chaos theory
auteur theory
cell theory
catastrophe theory
big bang theory
domino theory
devil theory
decision theory
conspiracy theory
critical race theory
graph theory
grand unified theory
germ theory
general theory of relativity
game theory
field theory
Galois theory
gauge theory
quantum theory
quantum field theory
group theory
information theory
queer theory
quantity theory
number theory
knot theory
kinetic theory
special theory of relativity
steady state theory
theory of games
string theory
theory of numbers
trickle - down theory
undulatory theory
wave theory

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Cite this Entry

“Theory.” Merriam-Webster.com Dictionary , Merriam-Webster, https://www.merriam-webster.com/dictionary/theory. Accessed 13 Apr. 2024.

Kids Definition

Kids definition of theory.

from Latin theoria "a looking at or considering of facts, theory," from Greek theōria "theory, action of viewing, consideration," from theōrein "to look at, consider," — related to theater

Medical Definition

Medical definition of theory, more from merriam-webster on theory.

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Why this eclipse could really show Einstein was correct

Five telescopes. four and a half minutes. one shot at getting data from the total solar eclipse..

EL SALTO, Mexico — Thirty minutes before totality, a large cloud dared to park in front of the sun. The sunlight split against the puffs to create a beautiful rainbow, but it was a nuisance for the more than 70 onlookers.

Granted they wanted the sun to be covered up, but by the moon, not a cloud.

“Got to get that cloud out of there. Move, cloud,” said Toby Dittrich, a physics professor at Portland Community College.

For him, the eclipse isn’t about the pictures of an occluded sun — although that’s enough for millions of other eclipse viewers gathering under its path from Mazatlán, Mexico, to Canada. Instead, he chose the outskirts of this small Mexican town because it was at the center of the eclipse shadow, providing about 4 minutes and 30 seconds of totality, enough to understand our universe like never before.

Dittrich, fellow physicists and student researchers were planning to run one of the most famous astronomical experiments in history — one that proved Albert Einstein’s theory of general relativity. It showed how our massive sun bends starlight around it, showing that space-time must be curved instead of flat as Isaac Newton had predicted. Since it was performed with rudimentary instruments in 1919, though, scientists have run only a limited number of loose follow-on tests.

Dittrich wanted to do better — and had the equipment for it. But in addition to the pesky cloud, there was another problem.

Six minutes before the eclipse, the students at telescope station No. 4 called for help. Its alignment was off, perhaps because of a faulty mount.

“I’m trying to save the station!” said their professor, Daniel Borrero Echeverry, shooing away the gathering crowd.

With a minute before totality, Borrero Echeverry was still frantically working at the telescope station. And the cloud was still there.

Planning to retire this year after 46 years, Dittrich, 77, had been chasing this eclipse data for eight years. “No one really believes that [Einstein’s theory] isn’t true because of theoretical calculations,” he said. “But no one has actually satisfactorily proven it” with data really close to the sun.

Now, he was nervous he wouldn’t either.

105 years before this eclipse

The inspiration for Dittrich’s 2024 experiment is traced back to more than a century ago. A 36-year-old Einstein, yet to reach major stardom, published a radical new idea in 1915 on how gravity worked.

Previously, Newton proposed that gravity occurred in a flat, uniform space. But in Einstein’s universe, space and time (which are inextricably linked together) are curved, getting pushed, pulled, stretched and warped by matter.

“If you get really close to really massive things, things get weird,” said Borrero Echeverry, a physics professor at Willamette University in Oregon.

Einstein did the math to demonstrate his theory, but he suggested one way of measuring it in the real world would be by recording the position of the stars close to the sun when the sun is out and compare it to when it’s absent. It’s difficult to observe stars in broad daylight because the sun washes them out, though — unless a total solar eclipse blocks the sun’s surface, allowing scientists to see details along its outer edge.

Einstein’s general relativity theory predicted that the massive sun should bend the light of surrounding stars by about twice as much as predicted per Newton’s theory — a change too small to detect with a human eye but potentially visible with telescopes at that time.

Enter British astronomers Sir Arthur Eddington and Frank Dyson. In 1919, they hauled their instruments from Britain to northern Brazil and West Africa to measure starlight during a total solar eclipse. They captured a total of 14 stars that showed the light deflection that Einstein predicted, although the margin of error was large.

Nonetheless, they proclaimed Einstein was correct, launching the physicist into the mainstream celebrity status that we know today. “EINSTEIN THEORY TRIUMPHS,” the New York Times wrote.

This eclipse, Dittrich, Borrero Echeverry and a handful of student and faculty researchers geared up to redo the 1919 Eddington experiment in unmatched detail with better ground telescopes and thousands of sky images. They specifically wanted to measure stars extremely close to the sun’s edge — the “forbidden zone” where they often get washed out by the bright sunlight.

7 years to the eclipse

This is no easy experiment. Over the years, several research teams have tried to re-create it, but they either failed, produced too large margins of error or didn’t capture enough data.

Dittrich and fellow physicist Richard Berry tried in August 2017, but it’s not something Dittrich really brags about. While the dataset was good, the calibration of his telescopes were off. His margin of error ended to be 50 percent, more than the original Eddington experiment. He attempted the experiment again during a total solar eclipse in Chile in December 2020, but rain and clouds got in the way.

Satellite missions and radio telescopes have made extremely precise measurements of starlight deflection over the past few decades, but none of these projects imaged stars in Dittrich’s coveted forbidden zone.

While it’s true that other expensive instruments have demonstrated this “gravitational lensing” with other galaxies , Dittrich wanted to do it with the sun using students and cheaper ground telescopes. Then it could also be replicated and added to physics curriculum in colleges.

The most promising Eddington experiment to date, by physicist and amateur astronomer Don Bruns, managed to capture 40 stars in the forbidden zone during the 2017 eclipse.

Equipped with 13 high-resolution telescopes with cameras deployed across Mexico and Texas, Dittrich’s 2024 team of student and faculty researchers could collect millions of data points that would offer a much sharper picture of this elusive forbidden zone than ever before: They expected to image 200,000 stars.

It’s like you’re painting a picture of a tree and all you have is a brown trunk, said Dittrich. More data from the forbidden zone would be like filling in details about that tree’s bark.

7 days to the eclipse

Traveling in his 1973 Volvo station wagon, Dittrich hauled a 10-foot trailer carrying about 800 pounds of equipment: tools, chairs, tables, laptops, cameras and five telescopes worth $11,000 total in boxes he custom-made.

Crossing the border into Mexico, Dittrich became scared that a federal officer who pulled him over might confiscate all that equipment — after all, the same thing happened to Eddington in 1914 en route to Crimea to conduct his experiment during World War I.

The officer let him through, not without taking the pesos out of Dittrich’s wallet and a handful of eclipse glasses.

Then fifty miles from El Salto, Dittrich’s Volvo broke down under the weight of the trailer and equipment. His car was towed to the town. He’ll have to pick it up in June, after he retires.

5 days to the eclipse

Once at their destination, an upscale neighborhood complex about 20 minutes away from El Salto, the team unloaded their boxes.

It took them about five full days at the site to prepare for the approximately 4 minutes and 30 seconds of full totality, not counting the months to years of preparation beforehand.

They mounted the telescopes, connected battery packs and upgraded the software to control their instruments and analyze the data. They assembled solar filters made from round cardboard oatmeal containers and galaxy-designed duct tape (totaling less than $20) to place over the expensive telescopes, so the instruments wouldn’t fry as they stared at the sun.

Then it was time to work out any kinks before the big show. Telescopes that were supposed to autonomously point to the North Star moved straight to ground: instrument error. Someone bumped a telescope, so it needed to be recalibrated: human error. The eclipse was hidden by clouds: an Earth error.

Sixteen hours before the eclipse, all five telescopes were detecting the starlight deflection to an accuracy of 0.05 arcseconds — a promising result that pointed to this being the most accurate Eddington experiment ever conducted.

Now, they just had to wait until 12:10 p.m. Central on Monday to see if it worked.

The countdown to totality

About two minutes before, Oliva Schutz, a third-year student at Willamette University on a telescope station, was feeling jittery.

“You’re not the one pressing the button on the computer,” fellow student Sam Jeffe told her, nervous. “If someone [messes] things up, it’s me.”

Borrero Echeverry had given up fixing telescope #4 at this point. He joined a group of at least 50 locals, who came to experience totality. Born and raised in Colombia, he began the countdown in Spanish.

“Siete! Seis! Cinco! Cuatro! Tres! Dos! Uno!” the crowd shouted in unison.

The sky darkened, and a glowing halo appeared in the sky. The crowd cheered, whistled and clapped.

“Oh my God!” said Jeffe. “And it’s clear around there!” The cloud appeared to be gone to human eyes.

“Stars!” another voice yelled.

Two bright dots appeared on either side of the eclipse, Jupiter and Venus. Borrero Echeverry spotted another bright dot, perhaps an eruption from the sun. Others saw small pink loops , called prominences, coming off the sun. On the ground, a sunset encircled the group.

“Check out your screens!” Cesar Delgado, a research assistant, said to Jeffe. Data started rolling in. The telescopes worked hard for four and a half minutes.

Then Borrero Echeverry started another group chant to mark the end: “Cinco! Cuatro! Tres! Dos! Uno!”

And just like that, totality was over.

After the eclipse

“It was insane,” said Maddie Strate, a first-year student at Willamette.

While everyone was abuzz, the students in charge of telescope station No. 4 sat quietly on the side. The team was unable to realign the telescope to the sun, only getting about 30 seconds of data.

“These are man-made machines, and man-made machines make mistakes that you can’t do anything about,” said Anna Hornbeck, a third-year physics major who was at the station.

The seven telescopes in Texas also hit roadblocks. Clouds covered the eclipse, so there was no data.

But the other four telescopes in El Salto got plenty of star data. It will take time to see how many of those were in the forbidden zone, but preliminary results look promising.

“I went through this monstrous trouble to get to Mexico, and it paid off,” Dittrich said.

2024 total solar eclipse

A total solar eclipse passed across the United States on Monday, April 8. See photos and videos from the path of totality and read our reporters’ coverage from scenes across the nation .

Looking ahead: Missed this one? The next eclipse visible in the United States won’t be until 2044 — and then we’ll see another shortly after in 2045. If you did watch this eclipse but without proper eyewear, here’s what to do if your eyes hurt .

The science: This eclipse appeared especially dramatic because the sun was at its most active period in two decades. In the past, solar eclipses have helped scientists learn more about the universe . Here’s everything else to know about the solar eclipse.

What to do if your eyes hurt after the eclipse and how to spot damage April 9, 2024 What to do if your eyes hurt after the eclipse and how to spot damage April 9, 2024
See how the eclipse transformed America, city by city April 8, 2024 See how the eclipse transformed America, city by city April 8, 2024
Clouds part and crowds scream as total solar eclipse delights the U.S. April 8, 2024 Clouds part and crowds scream as total solar eclipse delights the U.S. April 8, 2024

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Four Takeaways From the Vatican’s Document on Human Dignity

The document restated the Roman Catholic Church’s rejection of abortion, gender fluidity and transition surgery.

The pope speaking into a microphone while standing at a window at the Vatican with a red and white cloth hanging out.

By Jason Horowitz and Elisabetta Povoledo

Jason Horowitz reported from Rome, and Elisabetta Povoledo from Verbania, Italy.

The document issued on Monday by the Vatican puts human dignity at the center of Catholic life , but in doing so, it broaches some of the most difficult and sensitive social issues, those that Pope Francis has spent his papacy avoiding.

On Monday, though, his church leaned hard into them in the document, called “Infinite Dignity.” It argued that the exploitation of the poor, the outcast and the vulnerable amounted to an erosion of human dignity. But it was the restating of the church’s rejection of abortion, the death penalty and euthanasia, and especially gender fluidity, transition surgery and surrogacy, that church liberals worried would be used as ammunition by the right.

Here are four takeaways.

The pope’s inclusivity has limits.

Pope Francis’ inclusive message, which has included allowing L.G.B.T.Q. Catholics to receive blessings from priests and transgender people to be baptized and act as godparents , has a limit: Catholic doctrine.

The pope’s conservative critics have for a decade argued that his tendency to speak off the cuff and in overly welcoming ways toward L.G.B.T.Q. people, the divorced and remarried, along with others who sin in the church’s eyes, had sent the wrong signal.

But the document released on Monday, and remarks by Cardinal Víctor Manuel Fernández, the prefect of the Vatican department with oversight over doctrine, underlined that the pope’s message was just that — a signal that the church was more open to the world, but that the substance, what it considers immutable “truth,” remained the same.

That dissonance, though, between Francis’ style and his defense of Catholic doctrine was highlighted by the document, and for many supporters of great change within the church, it amounted to a declaration that they would not get what they want.

As if to highlight that tension, Cardinal Fernández responded to a question on Monday about the church’s teaching that homosexual acts are “intrinsically disordered” — what many supporters of L.G.B.T.Q. faithful consider the insurmountable obstacle to true acceptance — by saying that the problem may be the terminology, not the meaning.

It was, he said, a “very strong expression” and that perhaps “more suitable words” could be found to express the thought that homosexual sex could not produce the “mystery” of childbirth.

Gender fluidity erodes human dignity, the document says.

The Vatican argues that gender fluidity, or the idea that people can decide their own sex, erodes human dignity because it blurs the difference between men and women, which it considers a gift from God.

Francis, while personally welcoming to transgender people — he has met many throughout his papacy — is convinced that powerful lobbies are pushing what the Vatican calls “gender theory” as a form of “cultural colonization” on more traditionalist societies.

This ideology, the Vatican said in the document issued on Monday, “envisages a society without sexual differences, thereby eliminating the anthropological basis of the family.” It was unacceptable, the Vatican said, that such ideologies managed to “assert themselves as absolute and unquestionable, even dictating how children should be raised.”

The Vatican ties surrogacy to commercialization.

The Vatican document reiterates its opposition to surrogacy, arguing that even though the process may fulfill the wishes of couples longing to have children, it does so at the cost of a wider human dignity because it reduces women, in the Vatican’s view, to simply carriers and children to what Francis has called products of “commercialization.”

The church’s opposition to surrogacy and in vitro fertilization stems from its ethical and theological teachings on the issue of life. Though Francis has made it clear that while the church opposes surrogacy, children born from surrogacy can be baptized.

“First and foremost, the practice of surrogacy violates the dignity of the child,” who “has the right to have a fully human (and not artificially induced) origin and to receive the gift of a life that manifests both the dignity of the giver and that of the receiver,” the document states.

“Surrogacy also violates the dignity of the woman, whether she is coerced into it or chooses to subject herself to it freely,” as it detaches the women “from the child growing in her and becomes a mere means subservient to the arbitrary gain or desire of others.”

The sex a person is born with is seen as a gift from God.

The Vatican document is adamant in its rejection of transition surgeries, what it calls “Sex Change.” It argues that the physical sex a person is born with — male or female — is an equal gift from God, who has made the human in his image. It is not a gift you can give back, the Vatican says.

Changing sex, the church argues, is to put individualism before “the need to respect the natural order of the human person,” and “any sex-change intervention, as a rule, risks threatening the unique dignity the person has received from the moment of conception.”

The church, however, made an exception for people with “genital abnormalities that are already evident at birth or that develop later,” which could be resolved through “health care professionals” because it would “not constitute a sex change in the sense intended here.”

Jason Horowitz is the Rome bureau chief for The Times, covering Italy, the Vatican, Greece and other parts of Southern Europe. More about Jason Horowitz

Elisabetta Povoledo is a reporter based in Rome, covering Italy, the Vatican and the culture of the region. She has been a journalist for 35 years. More about Elisabetta Povoledo

Tennessee lawmakers vote to ban geoengineering, with allusions to 'chemtrails' conspiracy theory

contrails, contrail chemtrails airplace jet aircraft

The Tennessee state House of Representatives passed a bill Monday designed to prevent geoengineering, the practice of intentionally modifying the atmosphere to counteract global warming.

The bill, which had already passed in the state Senate, covers a variety of technological interventions. They include theoretical ideas about cooling the climate by an approach known as solar radiation modification, as well as more limited practices that affect the weather, like cloud seeding, a technique used to increase rain and snowfall.

Most geoengineering options are theoretical and untested. Federal researchers have taken only a few small steps toward studying their feasibility, and atmospheric scientists say there is no evidence of any large-scale programs.

On its face, Tennessee’s bill represents an attempt to prevent experimentation with or deployment of such technologies.

However, lawmakers’ discussions of the proposal toed a line between fact and fiction, with several suggesting that solar geoengineering projects are already underway and others referring to fears and misunderstandings that appeared to stem from the “chemtrails” conspiracy theory.

“This will be my wife’s favorite bill of the year. She has worried about this, I bet, 10 years. It’s been going on a long, long time,” Republican Sen. Frank Niceley said at a hearing about the bill last month. “If you look up — one day, it’ll be clear. The next day they will look like some angels have been playing tic-tac-toe. They’re everywhere. I’ve got pictures on my phone with X's right over my house. For years they denied they were doing anything.”

None of the six Senate sponsors responded to requests for comment. Niceley, who voted for the bill, also did not respond to a request for comment after the House vote. Rep. Monty Fritts, a Republican who sponsored the bill in the House, would agree only to an in-person interview, which NBC News was unable to arrange before the vote.

The chemtrails theory is a loose grouping of unfounded ideas that suggest planes are not making trails of condensation known as contrails but instead are spraying government-made chemicals to control people’s behavior or affect their bodies.

In recent years, some chemtrails conspiracy theories have evolved, with believers suggesting that contrails are actually aerosols designed to control the weather or the climate. The Tennessee Lookout, a nonprofit news organization, reported that Republican Sen. Steve Southerland, one of the sponsors, referred to the chemtrails theory when he presented his argument for the bill to a reporter.

Justin Mankin, a climate scientist at Dartmouth College, said: “It’s conspiratorial nonsense. The challenge here is that the whole chemtrails conspiracy has blurred and subsumed all these distinct technologies with distinct aims, which makes it challenging to disentangle.”

The Tennessee Legislature is not alone in its effort to enact anti-geoengineering policy. Lawmakers in Illinois, Kentucky, Minnesota, New Hampshire, Pennsylvania, Rhode Island and South Dakota have introduced or previewed similar bills.

The trend suggests that a mix of conspiracy theories, confusion and genuine concern about the possibility of climate modification has taken hold in the public consciousness — and among some Republican lawmakers.

“There are people in places like Tennessee and Pennsylvania and New Hampshire who are fearful that the chemtrails theory is correct,” Mankin said. “Policymakers, instead of relying on science to appropriately debunk conspiratorial belief, have rendered it legitimacy through legislative action.”

Josh Horton, a senior fellow who studies solar geoengineering policy at the Harvard Kennedy School, said that as far as he is aware, Tennessee is the first state to pass such a bill through both chambers of its legislature.

If the governor signs it into law, the bill would prohibit the “intentional injection, release or dispersion” of chemicals into the atmosphere for the “express purpose of affecting temperature, weather, or the intensity of the sunlight.”

The bill claims that “it is documented that the federal government” or those working on its behalf can “conduct geoengineering experiments by intentionally dispersing chemicals into the atmosphere.”

A White House official said in an email that “the federal government is not involved in any outdoor testing or deployment of solar radiation management.”

The official said the government “is engaged in a limited subset of research activities on this topic, including modeling, measurements and monitoring, and laboratory research.”

The Tennessee vote became contentious Monday evening.

Rep. John Ray Clemmons, a Democrat, poked fun at the bill, attaching an amendment that mimicked its original language but suggested that geoengineering “may threaten the Sasquatch and its natural habitat.” His amendment failed.

Another Democrat, Rep. Bo Mitchell, said: “It’s very appropriate this bill is on the calendar on April 1.”

However, Fritts, the House sponsor, pointed to federal funding for aerosol research as evidence of the government’s aims.

“There is an intent and a plan,” he said. “I suspect that some of those that have these plans with the solar radiation modification intend to try to reflect the sun’s rays from the Earth by injecting these chemicals, chemical compounds, substances and apparatus into the upper atmosphere.”

It is not surprising that lawmakers would struggle with key concepts of geoengineering. The term is overarching and poorly defined, and many of the ideas that fall under its umbrella are little more than the back-of-napkin sketches of scientists dreaming of ways to reduce global warming.

“It’s not fully formed. It doesn’t exist,” Horton said. “The terminology is all over the place.”

The broad category includes solar geoengineering, which the Tennessee bill would ban. The term refers to activities like stratospheric aerosol injections, an untested theory that the planet could be cooled by spraying particles into the stratosphere from high-altitude aircraft.

Other geoengineering concepts not mentioned in the bill include marine cloud brightening — using aerosols over the ocean in an effort to brighten clouds there — and cirrus cloud thinning, which refers to thinning certain icy clouds to allow more heat to escape Earth.

Tennessee’s bill would also outlaw weather modification, like cloud seeding, a decades-old practice used in Western states to encourage precipitation.

Some states regulate cloud seeding operations, which are usually small-scale efforts to increase snowfall in mountain ranges, but most other forms of geoengineering remain in a “regulatory Wild West,” Mankin said.

Committee hearings about the legislation yielded a confusing mix of truth, innuendo and fiction.

Dr. Denise Sibley, an advocate for the bill who testified before both chambers, suggested that the federal government has been seeding chemicals in the atmosphere.

“There is no doubt that weather modification is taking place within our state,” Sibley said, adding: “We do not consent to the intentional blocking of the sun through the use of particulate aerosols and heavy metals.”

She pointed Tennessee lawmakers to a 2023 White House report as evidence. The document discusses what a geoengineering research program could look like but does not outline an active program.

Sibley did not respond to requests for comment.

During the hearings, lawmakers also confused contrails with “chemtrails” and asked whether wildfires in Western states were caused by cloud seeding or whether geoengineering was causing a rise in cancer rates.

Republican Rep. Bud Hulsey inquired about whether geoengineering was the reason for honeybees’ decline.

“Absolutely — and it is the reason that the honeybees are going away,” replied David Perry, who was testifying in support of the bill and told the committee that he was a licensed health care provider of 40 years. “The microcosm that they live in is affected by these aerosols.”

There is no evidence to support Perry’s assertion. A Tennessee chiropractor of the same name who matched the biographical information Perry gave during his testimony did not immediately respond to a request for comment. Bees do face dire problems, including threats from pests , pesticides , reduced habitat and climate change.

“What you see is the mixing up and conflation of all these things — geoengineering is the same as weather modification is the same as chemtrails or contrails,” said Horton, who reviewed video of recent legislative testimony.

State Sen. Heidi Campbell, a Democrat, voted against the bill.

“It’s alarming although quite common around here to see people just wholesale buying into these conspiracy theories,” Campbell said, adding that she believed the bill was a distraction from core climate issues.

Mankin and Horton agreed that there are important conversations to have about how to guide and regulate research into solar geoengineering, which is controversial even among many scientists.

“Is the Tennessee state Legislature the place to have that conversation?” Horton said. “Probably not.”

Evan Bush is a science reporter for NBC News. He can be reached at [email protected].

3D mouth of an ancient jawless fish suggests they were filter-feeders, not scavengers or hunters

Early jawless fish were likely to have used bony projections surrounding their mouths to modify the mouth's shape while they collected food.

Experts led by the University of Birmingham have used CT scanning techniques to build up the first 3D pictures of these creatures, which are some of the earliest vertebrates (animals with backbones) in which the mouth is fossilised. Their aim was to answer questions about feeding in early vertebrates without jaws in the early Devonian epoch -- sometimes called the Age of Fishes -- around 400 million years ago.

Feeding behaviours are commonly used by scientists to help piece together early evolution of vertebrates, and different jaw shapes and constructions can suggest a broad range of feeding strategies. In the absence of jaws, many competing theories have been developed ranging from biting and slicing, to filtering food from sediment or water.

In a new study, published in Proceedings of the Royal Society B, an international team of palaeontologists have been able to visualise the mouth parts of one of these jawless fish, called Rhinopteraspis dunensis , in detail. The images revealed the structure and arrangement of finger-like bones that project from the lower 'lip' of the animal's mouth, which the scientists believe acted to control the mouth's size and shape as it captured food particles from surrounding water.

Senior author and project lead Dr Ivan Sansom said: "The application of CT scanning techniques to the study of fossil fish is revealing so much new information about these ancient vertebrates and giving us the opportunity to study precious and unique specimens without destructive investigation."

Lead author Dr Richard Dearden explained: "In this case, these methods have allowed us to fit all of the small bones of this animal's mouth together, and try and understand how it fed from this integrated system rather than by using isolated bones. Instead of a steady trend towards 'active food acquisition' -- scavenging or hunting -- we see a real diversity and range of feeding behaviours among our earliest vertebrate relatives."

The reconstruction produced by the team shows that the bony plates around the mouth would have had limited movement, making it unlikely that the animals were hunters capable of 'biting'. In combination with an elongated snout, they would also have found it difficult to scoop and filter sediment directly from the bottom of the sea. However these plates would have allowed it to control opening of the mouth, and perhaps strain food from water in a way also used by animals such as flamingos or oysters.

The findings offer a new perspective on theories of vertebrate evolution, since current hypotheses argue that long term evolutionary trends move from passive food consumption to increasingly predatory behaviour. In contrast, the work outlined in this paper suggests that in fact, early vertebrates had a broad range of different feeding behaviours long before jawed animals started to appear.

The study was funded by the Leverhulme Trust and is part of a collaborative project between the University of Birmingham, the Natural History Museum, and the University of Bristol, in the UK, and Naturalis Biodiversity Centre, in the Netherlands.

Food and Agriculture
Marine Biology
Agriculture and Food
Early Humans
Human Evolution

Story Source:

Materials provided by University of Birmingham . Note: Content may be edited for style and length.

Journal Reference :

Richard P. Dearden, Andy S. Jones, Sam Giles, Agnese Lanzetti, Madleen Grohganz, Zerina Johanson, Stephan Lautenschlager, Emma Randle, Philip C. J. Donoghue, Ivan J. Sansom. The three-dimensionally articulated oral apparatus of a Devonian heterostracan sheds light on feeding in Palaeozoic jawless fishes . Proceedings of the Royal Society B: Biological Sciences , 2024; 291 (2019) DOI: 10.1098/rspb.2023.2258

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The Vatican says surrogacy and gender theory are 'grave threats' to human dignity

Jason DeRose

The crowd looks in direction of the window of the apostolic palace overlooking St. Peter's square during Pope Francis' prayer on April 1 in The Vatican. TizianaI Fabi/AFP via Getty Images hide caption

The crowd looks in direction of the window of the apostolic palace overlooking St. Peter's square during Pope Francis' prayer on April 1 in The Vatican.

The Vatican has released a new document calling poverty, war and the plight of migrants "threats to human dignity." But it also calls abortion, surrogacy and gender theory "grave threats" facing humanity today.

The document, titled " Infinite Dignity " says that each person's dignity comes from the love of the creator "who has imprinted the indelible features of his image on every person." This language is familiar to Christians accustomed to hearing that humans are all made in God's image.

The document goes on to say that this dignity is inalienable, beyond any circumstance or situation the person might encounter. Simply put, because a person exists, a human has intrinsic dignity.

"Infinite Dignity" details a long list of what it calls grave threats to that dignity, some of which might be expected given other Catholic teachings. It talks about the drama of poverty and how the unequal distribution of wealth denies humans their God-given dignity. It also describes war, the abuse of migrants, sexual abuse, violence against women, the marginalizing of people with disabilities, assisted suicide and abortion all as affronts to human dignity.

But then the document turns to other issues that have become more highly politicized in recent years: surrogacy, gender theory, and what it calls "sex change."

The pope wants surrogacy banned. Here's why one advocate says that's misguided

The document's framework holds that if a person is made in God's image, gender theory and gender reassignment surgery call into question why God would create a person with the wrong gender.

It says that the understanding of humanity as divided into two sexes — male and female — is biblical and deeply meaningful, especially in terms of procreation. Gender theory argues that a person's gender can be different from the sex that person was assigned at birth.

"Infinite Dignity" says the concept of human dignity can be misused to justify what it calls an "arbitrary proliferation of new rights," describing those, rather, as "individual preference" or "desire." That language is very similar to how conservatives often talk about being transgender as a choice, which is something major medical and psychological groups dispute.

The document makes a clear distinction between the issue of sexual orientation (whether a person is gay, lesbian or bisexual) and the issue of gender identity (whether a person's sex assigned at birth matches what that person understands his or her gender to be).

The document will be seen by some more conservative Catholic as a win after years of feeling embattled during Pope Francis's leadership. Just last year, the Vatican said priests could baptize transgender Catholics and allowed for priests to bless people in same-sex relationships .

Catholic Church works to explain what same-sex blessings are and are not

But many transgender Catholics and their families as well as more progressive Catholics are displeased with "Infinite Dignity."

Executive director of the LGBTQ Catholic group New Ways Ministry, Francis DeBernardo says of the document, "When it gets to the section on people who are transgender or non-binary, it doesn't apply the principles of human dignity to them."

New Ways Ministry's mission is, in part, to help pastors and religious teachers better understand gender identity and sexuality. It also fosters, "holiness and wholeness within the Catholic LGBTQ+ community."

DeBernardo argues "Infinite Dignity" does not live up to its own name. "In a sense, it's not infinite dignity," he says. "It's a very limited dignity that the church is offering."

He fears this document will be used to further persecute transgender people, and he thinks it will cause transgender Catholics and their families to leave the church.

The Vatican says priests can baptize transgender people

DeBernardo also worries the sections on gender theory and what it calls "sex change" will eclipse what he describes as the very good parts of the document on war, poverty and migrants.

The group Catholics for Choice, is also disappointed and calls into question how the document was created. "Yet again," said the group's president Jamie Manson in a written statement, "a group of all-male, celibate clergymen are telling women and gender-expansive people that their lived experiences are not real or valid."

Catholics for Choice advocates within the church on a variety of issues regarding sexual and reproductive health, including abortion rights. The group holds – and argues that Catholic teaching supports – people's individual consciences should be their guide in such decisions.

"It is clear to me that the women and trans people who continue to identify as Catholic — despite documents like this completely disregarding our experiences — only do so because of a deep love for our faith and its traditions," continues Manson in her statement. "It is devastating that our leaders do not offer the same respect and love in return."

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1.1: Hypothesis, Theories, and Laws

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Learning Objectives

Describe the difference between hypothesis and theory as scientific terms.
Describe the difference between a theory and scientific law.

Although many have taken science classes throughout the course of their studies, people often have incorrect or misleading ideas about some of the most important and basic principles in science. Most students have heard of hypotheses, theories, and laws, but what do these terms really mean? Prior to reading this section, consider what you have learned about these terms before. What do these terms mean to you? What do you read that contradicts or supports what you thought?

What is a Fact?

A fact is a basic statement established by experiment or observation. All facts are true under the specific conditions of the observation.

What is a Hypothesis?

One of the most common terms used in science classes is a "hypothesis". The word can have many different definitions, depending on the context in which it is being used:

An educated guess: a scientific hypothesis provides a suggested solution based on evidence.
Prediction: if you have ever carried out a science experiment, you probably made this type of hypothesis when you predicted the outcome of your experiment.
Tentative or proposed explanation: hypotheses can be suggestions about why something is observed. In order for it to be scientific, however, a scientist must be able to test the explanation to see if it works and if it is able to correctly predict what will happen in a situation. For example, "if my hypothesis is correct, we should see ___ result when we perform ___ test."

A hypothesis is very tentative; it can be easily changed.

What is a Theory?

The United States National Academy of Sciences describes what a theory is as follows:

"Some scientific explanations are so well established that no new evidence is likely to alter them. The explanation becomes a scientific theory. In everyday language a theory means a hunch or speculation. Not so in science. In science, the word theory refers to a comprehensive explanation of an important feature of nature supported by facts gathered over time. Theories also allow scientists to make predictions about as yet unobserved phenomena."

"A scientific theory is a well-substantiated explanation of some aspect of the natural world, based on a body of facts that have been repeatedly confirmed through observation and experimentation. Such fact-supported theories are not "guesses" but reliable accounts of the real world. The theory of biological evolution is more than "just a theory." It is as factual an explanation of the universe as the atomic theory of matter (stating that everything is made of atoms) or the germ theory of disease (which states that many diseases are caused by germs). Our understanding of gravity is still a work in progress. But the phenomenon of gravity, like evolution, is an accepted fact.

Note some key features of theories that are important to understand from this description:

Theories are explanations of natural phenomena. They aren't predictions (although we may use theories to make predictions). They are explanations as to why we observe something.
Theories aren't likely to change. They have a large amount of support and are able to satisfactorily explain numerous observations. Theories can, indeed, be facts. Theories can change, but it is a long and difficult process. In order for a theory to change, there must be many observations or pieces of evidence that the theory cannot explain.
Theories are not guesses. The phrase "just a theory" has no room in science. To be a scientific theory carries a lot of weight; it is not just one person's idea about something

Theories aren't likely to change.

What is a Law?

Scientific laws are similar to scientific theories in that they are principles that can be used to predict the behavior of the natural world. Both scientific laws and scientific theories are typically well-supported by observations and/or experimental evidence. Usually scientific laws refer to rules for how nature will behave under certain conditions, frequently written as an equation. Scientific theories are more overarching explanations of how nature works and why it exhibits certain characteristics. As a comparison, theories explain why we observe what we do and laws describe what happens.

For example, around the year 1800, Jacques Charles and other scientists were working with gases to, among other reasons, improve the design of the hot air balloon. These scientists found, after many, many tests, that certain patterns existed in the observations on gas behavior. If the temperature of the gas is increased, the volume of the gas increased. This is known as a natural law. A law is a relationship that exists between variables in a group of data. Laws describe the patterns we see in large amounts of data, but do not describe why the patterns exist.

What is a Belief?

A belief is a statement that is not scientifically provable. Beliefs may or may not be incorrect; they just are outside the realm of science to explore.

Laws vs. Theories

A common misconception is that scientific theories are rudimentary ideas that will eventually graduate into scientific laws when enough data and evidence has accumulated. A theory does not change into a scientific law with the accumulation of new or better evidence. Remember, theories are explanations and laws are patterns we see in large amounts of data, frequently written as an equation. A theory will always remain a theory; a law will always remain a law.

Video $\PageIndex{1}$: What’s the difference between a scientific law and theory?

A hypothesis is a tentative explanation that can be tested by further investigation.
A theory is a well-supported explanation of observations.
A scientific law is a statement that summarizes the relationship between variables.
An experiment is a controlled method of testing a hypothesis.

Contributions & Attributions

Marisa Alviar-Agnew ( Sacramento City College )

Henry Agnew (UC Davis)

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3.1.3: Developing Theories and Hypotheses

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2.5: Developing a Hypothesis

Learning objectives.

Distinguish between a theory and a hypothesis.
Discover how theories are used to generate hypotheses and how the results of studies can be used to further inform theories.
Understand the characteristics of a good hypothesis.

Theories and Hypotheses

Theory Testing

The primary way that scientific researchers use theories is sometimes called the hypothetico-deductive method (although this term is much more likely to be used by philosophers of science than by scientists themselves). Researchers begin with a set of phenomena and either construct a theory to explain or interpret them or choose an existing theory to work with. They then make a prediction about some new phenomenon that should be observed if the theory is correct. Again, this prediction is called a hypothesis. The researchers then conduct an empirical study to test the hypothesis. Finally, they reevaluate the theory in light of the new results and revise it if necessary. This process is usually conceptualized as a cycle because the researchers can then derive a new hypothesis from the revised theory, conduct a new empirical study to test the hypothesis, and so on. As Figure $\PageIndex{1}$ shows, this approach meshes nicely with the model of scientific research in psychology presented earlier in the textbook—creating a more detailed model of “theoretically motivated” or “theory-driven” research.

Incorporating Theory into Your Research

Zajonc, R. B. (1965). Social facilitation. Science, 149 , 269–274 ↵
Schwarz, N., Bless, H., Strack, F., Klumpp, G., Rittenauer-Schatka, H., & Simons, A. (1991). Ease of retrieval as information: Another look at the availability heuristic. Journal of Personality and Social Psychology, 61 , 195–202. ↵
Zajonc, R. B., Heingartner, A., & Herman, E. M. (1969). Social enhancement and impairment of performance in the cockroach. Journal of Personality and Social Psychology, 13 , 83–92. ↵
Zajonc, R.B. & Sales, S.M. (1966). Social facilitation of dominant and subordinate responses. Journal of Experimental Social Psychology, 2 , 160-168. ↵

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Theories that explain the crisis in democracy are inadequate for Latin America, experts say

by Elton Alisson, FAPESP

The theories offered by the dominant literature in political science today to try to explain the sources of the political polarization that has endangered democracy around the world are adequate for the United States and Europe, but do not make sense for the countries of Latin America. For this reason, greater collaboration among political scientists is needed to identify other, more plausible hypotheses for the phenomenon that the region is also experiencing.

The assessment was made by researchers participating in a panel discussion on democracy and social inclusion held on April 9 in Chicago (United States) during FAPESP Week Illinois .

"There's an avenue for possible research collaboration between Latin American and North American political scientists, for example, to advance in identifying the sources of political polarization in the two regions and to overcome this challenge in the literature. We have a lot of data and interest in working together to better understand this phenomenon," said Marta Arretche, professor at the University of São Paulo (USP) in Brazil and researcher at the Center for Metropolitan Studies (CEM)—a FAPESP Research, Innovation and Dissemination Center (RIDC).

According to the researcher, the most influential literature in the social sciences today, mainly in the United States and Europe, establishes a positive link between social inequality and political polarization to explain the rise in electoral strength of extreme right-wing parties and the threats to democratic institutions.

According to this theory, wealthier democracies have experienced an increase in social inequality, which would be the cause of voter support for the proposals of far-right parties.

"According to this theory, the left-wing parties have somehow abandoned their traditional electorate and implemented pro-rich policies, and so the right-wing parties have exploited the discontent of the poorest, who have lost out in the current democratic regimes. But recent research in Latin America, and Brazil in particular, provides good evidence that this may not be true for countries in the region," Arretche said.

Ongoing postdoctoral research at the CEM on the determinants of political polarization in Latin America shows that although the Gini index (a measure of social inequality) has decreased since the early 2000s, political polarization in Latin American countries has increased over the same period.

"There's evidence for Latin America that doesn't confirm the positive association between increases in inequality and increases in polarization. On the contrary, it shows a negative association," Arretche said.

Another study , available as a working paper on the SSRN Electronic Journal and also conducted by Brazilian political scientists , on how the perception of gaining or losing social status influences the political positions of the Brazilian electorate, showed that those who vote for left-wing parties in the country are those who believe they have gained centrality in the political arena in the last 20 years. On the other hand, those who voted for right-wing parties perceive themselves as having lost centrality in recent years.

"The conclusion of the authors of this study also goes in the opposite direction of the dominant literature on the United States and Europe. They conclude that the progressive policies implemented by left-wing parties in Brazil since the early 2000s have shaped the political divide that exists today," Arretche explains.

On the other hand, another ongoing study conducted by the researcher and her collaborators also provides some evidence of disenchantment among Workers' Party (PT) voters in recent years.

"The party has lost support among its own voters during the crises that Brazil has gone through in the last five years," Arretche said.

Political crisis

The changes that have taken place in Brazil since 2013, marked by a very intense political crisis, have changed the behavior of actors and generated instability in the pillars of coalition presidentialism in the country, pointed out Andrea Freitas, coordinator of the Center for Public Opinion Studies at the State University of Campinas (CESOP-UNICAMP).

This parliamentary regime that exists in Brazil and other countries, in which the president tries to form coalitions because he doesn't have a majority in the legislature, could change its configuration in the country, the researcher said.

"My hypothesis is that given the long period of political crisis that Brazil has gone through in the last ten years, there's been a real change in the behavior of political actors in the country, and we're no longer going back to the same institutional bases of coalition presidentialism. We're going to have to build a different relationship," Freitas said.

Health inequalities

Brazil and other countries have also undergone transformations in other areas, such as health, that may contribute to increasing levels of inequality in the country, explained Rudi Rocha, a professor at the Getúlio Vargas Foundation (FGV) in São Paulo.

One of these changes is the aging of the population, which means that health systems not only in Brazil but in many other countries will have to deal with an increasing number of chronic diseases and other conditions that are more expensive to treat, Rocha noted.

"In the past, health systems in countries like Brazil only had to deal with childhood infectious diseases, which are cheap to treat through vaccination, for example. Now, in low- and middle-income countries, inequalities will eventually increase if they don't have the capacity to meet the challenges of an aging population," he said.

The public sector's difficulty in raising sufficient funds to meet health care needs opens up opportunities for the private sector to enter and expand its presence, the researcher pointed out.

"This is already happening in many places around the world, and it could also be a vector of inequality. Ultimately, only those who can afford it will have access to private health care," Rocha said.

Another vector of social inequality in the country is climate change , which has a more direct impact on poor people, who don't have access to health care, the researcher stressed.

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Theory vs. Hypothesis: Basics of the Scientific Method
A hypothesis proposes a tentative explanation or prediction. A scientist bases their hypothesis on a specific observed event, making an educated guess as to how or why that event occurs. Their hypothesis may be proven true or false by testing and experimentation. A theory, on the other hand, is a substantiated explanation for an occurrence.
Hypothesis vs. Theory: The Difference Explained
What to Know. A hypothesis is an assumption made before any research has been done. It is formed so that it can be tested to see if it might be true. A theory is a principle formed to explain the things already shown in data. Because of the rigors of experiment and control, it is much more likely that a theory will be true than a hypothesis.
Hypothesis vs Theory
A hypothesis is either a suggested explanation for an observable phenomenon, or a reasoned prediction of a possible causal correlation among multiple phenomena. In science, a theory is a tested, well-substantiated, unifying explanation for a set of verified, proven factors. A theory is always backed by evidence; a hypothesis is only a suggested possible outcome, and is testable and falsifiable.
Scientific hypothesis
hypothesis. science. scientific hypothesis, an idea that proposes a tentative explanation about a phenomenon or a narrow set of phenomena observed in the natural world. The two primary features of a scientific hypothesis are falsifiability and testability, which are reflected in an "If…then" statement summarizing the idea and in the ...
Hypothesis vs. Theory: Understanding Scientific Concepts
Hypothesis vs Thesis. A hypothesis is a specific, testable prediction that is proposed before conducting a research study, while a thesis is a statement or theory put forward to be maintained or proved. In essence, a hypothesis is a tentative assumption made in order to draw out and test its logical or empirical consequences, while a thesis is ...
"Theory" vs. "Hypothesis": What Is The Difference?
How to use each. Although theory in terms of science is used to express something based on extensive research and experimentation, typically in everyday life, theory is used more casually to express an educated guess. So in casual language, theory and hypothesis are more likely to be used interchangeably to express an idea or speculation.
What is a Hypothesis
The purpose of a hypothesis is to provide a testable explanation for an observed phenomenon or a prediction of a future outcome based on existing knowledge or theories. A hypothesis is an essential part of the scientific method and helps to guide the research process by providing a clear focus for investigation.
Developing Theories & Hypotheses
Theories and Hypotheses. Before describing how to develop a hypothesis, it is important to distinguish between a theory and a hypothesis. A theory is a coherent explanation or interpretation of one or more phenomena. Although theories can take a variety of forms, one thing they have in common is that they go beyond the phenomena they explain by including variables, structures, processes ...
Primary Difference Between Hypothesis and Theory
Hypothesis & theory have one main difference. Use these definitions & examples to explore how these terms differ from each other and similar science terms. ... Both theories and hypotheses are usually based on some date and can be tested. This means either could be substantiated or falsified.
How to Write a Strong Hypothesis
5. Phrase your hypothesis in three ways. To identify the variables, you can write a simple prediction in if…then form. The first part of the sentence states the independent variable and the second part states the dependent variable. If a first-year student starts attending more lectures, then their exam scores will improve.
1.2: Theories, Hypotheses and Models
A "hypothesis" is a consequence of the theory that one can test. From Chloë's Theory, we have the hypothesis that an object will take 2-√ 2 times longer to fall from 1m 1 m than from 2 m 2 m. We can formulate the hypothesis based on the theory and then test that hypothesis. If the hypothesis is found to be invalidated by experiment ...
1.6: Hypothesis, Theories, and Laws
1.6: Hypothesis, Theories, and Laws is shared under a CK-12 license and was authored, remixed, and/or curated by Marisa Alviar-Agnew & Henry Agnew. Although many have taken science classes throughout the course of their studies, people often have incorrect or misleading ideas about some of the most important and basic principles in science.
1.3: Hypothesis, Theories, and Laws
Henry Agnew (UC Davis) 1.3: Hypothesis, Theories, and Laws is shared under a license and was authored, remixed, and/or curated by LibreTexts. Although all of us have taken science classes throughout the course of our study, many people have incorrect or misleading ideas about some of the most important and basic principles in science. We ….
Developing a Hypothesis
Theories and Hypotheses. Before describing how to develop a hypothesis, it is important to distinguish between a theory and a hypothesis. A theory is a coherent explanation or interpretation of one or more phenomena. Although theories can take a variety of forms, one thing they have in common is that they go beyond the phenomena they explain by including variables, structures, processes ...
Developing a Hypothesis
Theories and Hypotheses. Before describing how to develop a hypothesis, it is important to distinguish between a theory and a hypothesis. A theory is a coherent explanation or interpretation of one or more phenomena. Although theories can take a variety of forms, one thing they have in common is that they go beyond the phenomena they explain by including variables, structures, processes ...
Research Hypothesis In Psychology: Types, & Examples
A research hypothesis, in its plural form "hypotheses," is a specific, testable prediction about the anticipated results of a study, established at its outset. It is a key component of the scientific method. Hypotheses connect theory to data and guide the research process towards expanding scientific understanding.
Hypothesis vs. Theory: A Simple Guide to Tell Them Apart
A hypothesis is an educated guess or a proposed explanation for an observation or phenomenon. It is a tentative explanation that can be tested through experiments and observations. On the other hand, a theory is a well-established explanation that has been supported by a large body of evidence.
Hypothesis Testing
It is most often used by scientists to test specific predictions, called hypotheses, that arise from theories. There are 5 main steps in hypothesis testing: State your research hypothesis as a null hypothesis and alternate hypothesis (H o) and (H a or H 1). Collect data in a way designed to test the hypothesis. Perform an appropriate ...
Difference Between Theory and Hypothesis -A Comparison Chart
A hypothesis is an educated guess based on certain data that acts as a foundation for further investigation. It is based on extensive data. It is based on limited data. A theory is proven and tested scientifically. A hypothesis is not proven scientifically. The results are certain. The results are uncertain. It relies on evidence and verification.
How to Write a Great Hypothesis
What is a hypothesis and how can you write a great one for your research? A hypothesis is a tentative statement about the relationship between two or more variables that can be tested empirically. Find out how to formulate a clear, specific, and testable hypothesis with examples and tips from Verywell Mind, a trusted source of psychology and mental health information.
Theories Definition & Meaning
The meaning of THEORY is a plausible or scientifically acceptable general principle or body of principles offered to explain phenomena. How to use theory in a sentence. The Difference Between Hypothesis and Theory Two Related, Yet Distinct, Meanings of Theory Synonym Discussion of Theory.
Why this eclipse could really prove Einstein was correct
Dittrich, fellow physicists and student researchers were planning to run one of the most famous astronomical experiments in history — one that proved Albert Einstein's theory of general ...
Four Takeaways From the Vatican's Document on Human Dignity
The document issued on Monday by the Vatican puts human dignity at the center of Catholic life, but in doing so, it broaches some of the most difficult and sensitive social issues, those that Pope ...
Tennessee lawmakers vote to ban geoengineering, with allusions to
The chemtrails theory is a loose grouping of unfounded ideas that suggest planes are not making trails of condensation known as contrails but instead are spraying government-made chemicals to ...
3D mouth of an ancient jawless fish suggests they were filter-feeders
The findings offer a new perspective on theories of vertebrate evolution, since current hypotheses argue that long term evolutionary trends move from passive food consumption to increasingly ...
Vatican says sex change, gender theory are 'grave threats' : NPR
The Vatican has released a new document calling poverty, war and the plight of migrants "threats to human dignity." But it also calls abortion, surrogacy and gender theory "grave threats" facing ...
1.1: Hypothesis, Theories, and Laws
Henry Agnew (UC Davis) 1.1: Hypothesis, Theories, and Laws is shared under a not declared license and was authored, remixed, and/or curated by LibreTexts. Although all of us have taken science classes throughout the course of our study, many people have incorrect or misleading ideas about some of the most important and basic principles in science.
3.1.3: Developing Theories and Hypotheses
Theories and Hypotheses. Before describing how to develop a hypothesis, it is important to distinguish between a theory and a hypothesis. A theory is a coherent explanation or interpretation of one or more phenomena. Although theories can take a variety of forms, one thing they have in common is that they go beyond the phenomena they explain by including variables, structures, processes ...
Theories that explain the crisis in democracy are inadequate for Latin
The theories offered by the dominant literature in political science today to try to explain the sources of the political polarization that has endangered democracy around the world are adequate ...
Vatican rejects gender-affirming surgery and surrogacy in new document
The Vatican on Monday reaffirmed its opposition to gender-affirming surgery, "gender theory" and surrogate parenthood, drawing criticism from advocates for LGBTQ Catholics.

Hypothesis vs. Theory

Comparison chart

Common Misconception

Related Comparisons

Comments: Hypothesis vs Theory

“Theory” vs. “Hypothesis”: What Is The Difference?

What does theory mean?

What does hypothesis mean?

How to use each

WATCH: "Lethologica" vs. "Lethonomia": What's The Difference?

What is a Hypothesis – Types, Examples and Writing Guide

Types of Hypothesis

Research Hypothesis

Null Hypothesis

Alternative Hypothesis

Directional Hypothesis

Non-directional Hypothesis

Statistical Hypothesis

Composite Hypothesis

Empirical Hypothesis

Simple Hypothesis

Complex Hypothesis

Applications of Hypothesis

How to write a Hypothesis

Identify the Research Question

Conduct a Literature Review

Determine the Variables

Formulate the Hypothesis

Write the Null Hypothesis

Refine the Hypothesis

Examples of Hypothesis

Purpose of Hypothesis

When to use Hypothesis

Characteristics of Hypothesis

Advantages of Hypothesis

Limitations of Hypothesis

About the author

Muhammad Hassan

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1.2: Theories, Hypotheses and Models

Emma's Thoughts

Exercise \(\PageIndex{2}\)

Developing a Hypothesis

Learning Objectives

Theories and Hypotheses

Theory Testing

Incorporating Theory into Your Research

Characteristics of a Good Hypothesis

Share This Book

10 Developing a Hypothesis

Theories and Hypotheses

Theory Testing

Incorporating Theory into Your Research

Characteristics of a Good Hypothesis

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Research Hypothesis In Psychology: Types, & Examples

Some key points about hypotheses:

Types of Research Hypotheses

Null Hypothesis

Nondirectional Hypothesis

Directional Hypothesis

Falsifiability

Can a Hypothesis be Proven?

How to Write a Hypothesis

More Examples

Hypothesis vs. Theory: A Simple Guide to Tell Them Apart

Hypothesis vs. Theory: Definitions

Understanding Theory

Hypothesis vs. Theory: The Distinctions

Process of Formulation

Level of Proof

Usage in Scientific Community

Hypothesis vs. Theory: Common Misconceptions

Frequently Asked Questions