Examples Of A Hypothesis Statement

By Science Buddies on February 23, 2010 9:23 AM


"If _____[I do this] _____, then _____[this]_____ will happen."


Sound familiar? It should. This formulaic approach to making a statement about what you "think" will happen is the basis of most science fair projects and much scientific exploration.

Step by Step
You can see from the basic outline of the Scientific Method below that writing your hypothesis comes early in the process:
  1. Ask a Question
  2. Do Background Research
  3. Construct a Hypothesis
  4. Test Your Hypothesis by Doing an Experiment
  5. Analyze Your Data and Draw a Conclusion
  6. Communicate Your Results

Following the scientific method, we come up with a question that we want to answer, we do some initial research, and then before we set out to answer the question by performing an experiment and observing what happens, we first clearly identify what we "think" will happen.

We make an "educated guess."

We write a hypothesis.

We set out to prove or disprove the hypothesis.

What you "think" will happen, of course, should be based on your preliminary research and your understanding of the science and scientific principles involved in your proposed experiment or study. In other words, you don't simply "guess." You're not taking a shot in the dark. You're not pulling your statement out of thin air. Instead, you make an "educated guess" based on what you already know and what you have already learned from your research.

If you keep in mind the format of a well-constructed hypothesis, you should find that writing your hypothesis is not difficult to do. You'll also find that in order to write a solid hypothesis, you need to understand what your variables are for your project. It's all connected!

If I never water my plant, it will dry out and die.

That seems like an obvious statement, right? The above hypothesis is too simplistic for most middle- to upper-grade science projects, however. As you work on deciding what question you will explore, you should be looking for something for which the answer is not already obvious or already known (to you). When you write your hypothesis, it should be based on your "educated guess" not on known data. Similarly, the hypothesis should be written before you begin your experimental procedures—not after the fact.



Hypotheses Tips

Our staff scientists offer the following tips for thinking about and writing good hypotheses.

  • The question comes first. Before you make a hypothesis, you have to clearly identify the question you are interested in studying.
  • A hypothesis is a statement, not a question. Your hypothesis is not the scientific question in your project. The hypothesis is an educated, testable prediction about what will happen.
  • Make it clear. A good hypothesis is written in clear and simple language. Reading your hypothesis should tell a teacher or judge exactly what you thought was going to happen when you started your project.
  • Keep the variables in mind. A good hypothesis defines the variables in easy-to-measure terms, like who the participants are, what changes during the testing, and what the effect of the changes will be. (For more information about identifying variables, see: Variables in Your Science Fair Project.)
  • Make sure your hypothesis is "testable." To prove or disprove your hypothesis, you need to be able to do an experiment and take measurements or make observations to see how two things (your variables) are related. You should also be able to repeat your experiment over and over again, if necessary.

    To create a "testable" hypothesis make sure you have done all of these things:

    • Thought about what experiments you will need to carry out to do the test.
    • Identified the variables in the project.
    • Included the independent and dependent variables in the hypothesis statement. (This helps ensure that your statement is specific enough.
  • Do your research. You may find many studies similar to yours have already been conducted. What you learn from available research and data can help you shape your project and hypothesis.
  • Don't bite off more than you can chew! Answering some scientific questions can involve more than one experiment, each with its own hypothesis. Make sure your hypothesis is a specific statement relating to a single experiment.


Putting it in Action

To help demonstrate the above principles and techniques for developing and writing solid, specific, and testable hypotheses, Sandra and Kristin, two of our staff scientists, offer the following good and bad examples.

Good HypothesisPoor Hypothesis
When there is less oxygen in the water, rainbow trout suffer more lice.

Kristin says: "This hypothesis is good because it is testable, simple, written as a statement, and establishes the participants (trout), variables (oxygen in water, and numbers of lice), and predicts effect (as oxygen levels go down, the numbers of lice go up)."

Our universe is surrounded by another, larger universe, with which we can have absolutely no contact.

Kristin says: "This statement may or may not be true, but it is not a scientific hypothesis. By its very nature, it is not testable. There are no observations that a scientist can make to tell whether or not the hypothesis is correct. This statement is speculation, not a hypothesis."

Aphid-infected plants that are exposed to ladybugs will have fewer aphids after a week than aphid-infected plants which are left untreated.

Sandra says: "This hypothesis gives a clear indication of what is to be tested (the ability of ladybugs to curb an aphid infestation), is a manageable size for a single experiment, mentions the independent variable (ladybugs) and the dependent variable (number of aphids), and predicts the effect (exposure to ladybugs reduces the number of aphids)."

Ladybugs are a good natural pesticide for treating aphid infected plants.

Sandra says: "This statement is not 'bite size.' Whether or not something is a 'good natural pesticide' is too vague for a science fair project. There is no clear indication of what will be measured to evaluate the prediction."



Hypotheses in History

Throughout history, scientists have posed hypotheses and then set out to prove or disprove them. Staff Scientist Dave reminds that scientific experiments become a dialogue between and among scientists and that hypotheses are rarely (if ever) "eternal." In other words, even a hypothesis that is proven true may be displaced by the next set of research on a similar topic, whether that research appears a month or a hundred years later.

A look at the work of Sir Isaac Newton and Albert Einstein, more than 100 years apart, shows good hypothesis-writing in action.

As Dave explains, "A hypothesis is a possible explanation for something that is observed in nature. For example, it is a common observation that objects that are thrown into the air fall toward the earth. Sir Isaac Newton (1643-1727) put forth a hypothesis to explain this observation, which might be stated as 'objects with mass attract each other through a gravitational field.'"

Newton's hypothesis demonstrates the techniques for writing a good hypothesis: It is testable. It is simple. It is universal. It allows for predictions that will occur in new circumstances. It builds upon previously accumulated knowledge (e.g., Newton's work explained the observed orbits of the planets).

"As it turns out, despite its incredible explanatory power, Newton's hypothesis was wrong," says Dave. "Albert Einstein (1879-1955) provided a hypothesis that is closer to the truth, which can be stated as 'objects with mass cause space to bend.' This hypothesis discards the idea of a gravitational field and introduces the concept of space as bendable. Like Newton's hypothesis, the one offered by Einstein has all of the characteristics of a good hypothesis."

"Like all scientific ideas and explanations," says Dave, "hypotheses are all partial and temporary, lasting just until a better one comes along."

That's good news for scientists of all ages. There are always questions to answer and educated guesses to make!



If your science fair is over, leave a comment here to let us know what your hypothesis was for your project.

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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. For example, 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."

Let's take a closer look at how a hypothesis is used, formed, and tested in scientific research.

How Is a Hypothesis Used 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:

  1. Forming a question
  2. Performing background research
  3. Creating a hypothesis
  4. Designing an experiment
  5. Collecting data
  6. Analyzing the results
  7. Drawing conclusions
  8. Communicating the results

The hypothesis is what the researchers' predict the relationship between two or more variables, 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.

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.

Unless you are creating a study that is exploratory in nature, your hypothesis should always explain what you expect to happen during the course of your experiment or research.

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.

How Do Researchers Come Up With a Hypothesis?

There are many ways to come up with a hypothesis. 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 for a specific hypothesis that: "People with high-stress levels will be more likely to contract a common cold after being exposed to the virus than are 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

When trying to come up with a good hypothesis for your own research or experiments, ask yourself the following questions:

  • Is your hypothesis based on your research of 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 on your topic. 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.

How to Form a Hypothesis

The first step of a psychological investigation is to identify an area of interest and develop a hypothesis that can then be tested. While a hypothesis is often described as a hunch or a guess, it is actually much more specific. A hypothesis can be defined as an educated guess about the relationship between two or more variables.

For example, a researcher might be interested in the relationship between study habits and test anxiety.

They would then propose a hypothesis about how these two variables are related, such as "test anxiety decreases as a result of effective study habits."

In order to form a hypothesis, you should:

  • Start by collecting as many observations about something as you can
  • Next, it is important to 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, it is important to think of ways that you could confirm or disprove each hypothesis through experimentation.

In the scientific methodfalsifiability is an important part of any valid hypothesis. This does not mean that the hypothesis is false; instead, it suggests that if the hypothesis were false, researchers could demonstrate this falsehood.

In order to test a claim scientifically, it must be possible that the claim could also be proven false. One of the hallmarks of a pseudoscience is that it makes claims that cannot be refuted or 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.

The Role of Operational Definitions

In the previous example, study habits and test anxiety are the two variables in this imaginary study. 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 exactly what each variable is using what is known as operational definitions. These definitions explain how the variable will be manipulated and measured in the study.

In our previous example, a researcher might operationally define the variable 'test anxiety' as the results on a self-report measure of anxiety experienced during an exam. The variable ‘study habits’ might be defined by the amount of studying that actually occurs as measured by time.

Why do psychologists and other researchers need to provide operational definitions for each variable? These precise descriptions of each variable 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.

Examples

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 make changes to 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:

  • "Students who eat breakfast will perform better on a math exam than students who do not eat breakfast."
  • "Students who experience test anxiety prior to an English exam will get higher 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."

A 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 Next Step: Collecting Data

Once a researcher has formed a testable hypothesis, the next step is to select a research design and start collecting data. The research method a researcher chooses 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. That is to say that if 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 some cases, the original hypothesis will be supported and the researchers will find evidence supporting their expectations about the nature of the relationship between different variables. In other situations, the results of the study might fail to support the original hypothesis.

Even in situations where the hypothesis is unsupported by the research, this does not mean that the research is without value. Not only does such research help 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 future research.

Sources:

Nevid, J. Psychology: Concepts and applications. Belmont, CA: Wadworth; 2013.

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