In any industry, the ability to use observations and create a compelling hypothesis to solve a problem through research is very valuable. Scientists, data analysts, and medical professionals should all learn how to write a hypothesis to guide their research. A good hypothesis is a key part of using research methods that lead to impactful research.
In this guide, we’ll define a hypothesis and the elements that make a complete hypothesis. We’ll also cover a couple of hypothesis examples and answer questions about creating a hypothesis. By the time you are done reading this article, you’ll know how to write a hypothesis that is perfect for any research project or empirical research paper.
What Is a Hypothesis?
A hypothesis is a testable statement used in research, and researchers use the hypothesis to design an experiment that will give results that support or do not support the hypothesis. People make causal hypotheses all the time when solving problems. For example, if you have an assumption that if you restart your computer it will fix the problem you’re having with a program, that statement is testable, because you can restart your computer and see if it fixes the problem.
What Are the Elements of a Hypothesis?
- Statement of the research question. A hypothesis is the research question rewritten as a testable statement. You have to include the goal of the research, the variables, the relationship between variables, and a testable prediction. Without a clear research question, you could end up performing endless, aimless research studies.
- Independent variable. The independent variable is the part of the experiment where you change something. If you are wondering whether different types of motor oil change your car’s mileage, motor oil is the independent variable. This is usually based on an idea that you came up with to solve a problem.
- Dependent variable. The dependent variable is the part of the experiment where you measure the outcome and collect data. In the above example about motor oil, the dependent variable is the car’s mileage because that is what you are measuring.
- Predicted relationship between the independent and dependent variable. The goal of your hypothesis is to make an educated guess of what impact the independent variable has on the dependent variable. You can hypothesize that different kinds of motor oil will have no effect on a car’s mileage, or that one kind of motor oil will increase the car’s mileage. This is also the declarative statement.
- Testability. You have to be able to test your hypothesis through experimentation. A hypothesis like, “Unicorns prefer to eat cake instead of cookies,” isn’t testable because there aren’t any unicorns to do the experiment with.
How to Write a Hypothesis: Beginning and Ending
To write a solid hypothesis you need to understand the scientific method and the basic format of a hypothesis. A strong, testable hypothesis turns random ideas into scientific experiments. A well-written hypothesis is usually a single sentence. Let’s look at how to start and end a strong hypothesis.
How to Begin a Hypothesis
The beginning of your hypothesis introduces the variables. Remember, the independent variable is the thing you change in your experiment and the dependent variable is the thing you measure. In the example, “Flowers watered with lemonade will grow faster than flowers watered with plain water,” water and lemonade are the independent variables and flowers’ growth rate is the dependent variable.
Many people choose to structure hypotheses as an if-then statement. For instance, “If you drink coffee before going to bed, then it will take you longer to fall asleep.” If you are having trouble with the process of hypothesis writing, then you should try starting with an if-then statement.
How to End a Hypothesis
The second section of a simple hypothesis statement is where you predict the relationship between the types of variables. Using our coffee example above, the second half of the sentence shows how we expect the amount of coffee to impact the time it takes to fall asleep.
When you write your prediction, remember to ask yourself, “Is this hypothesis testable?” You can predict that there is no relationship between your variables, that the independent variable will have an effect on the dependent variable, or you can make a specific guess about how the independent variable will affect the dependent variable. Bad hypotheses are not testable, because there is no way to prove or disprove your original idea.
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How to Write a Hypothesis: 5 More Useful Tips
Conduct preliminary research
To create a scientific hypothesis, you need to get background knowledge on your topic by reading previous studies, scientific experiments, and academic journals. You need to become a student of the sciences again. Be open-minded and explore research that supports and doesn’t support your ideas. Learn about the experimental methods other people use, and find any knowledge gaps that you could fill with your research question.
Define a research question
The first step in formulating a hypothesis is to brainstorm a research question. Use your writing skills to write a research question that’s specific, clear, focused, and manageable. Make sure you have the resources to conduct whatever experiment you’ll need to answer the question.
Formulate a hypothesis
Use your new background knowledge to rewrite your research question as a testable statement. Remember to include an independent variable, a dependent variable, and predict how they are related. Use an if-then statement if you are having trouble.
Refine your hypothesis
The first draft of a hypothesis is rarely perfect. You’ll need to edit and proofread to find and fix mistakes. Make sure your hypothesis is testable and has all the relevant variables. Try to get a peer or advisor to read your hypothesis and suggest changes.
Create a null and alternative hypothesis
A null hypothesis always states that there is no relationship between variables, while an alternative hypothesis states there is some kind of relationship between variables. You need to write both a null and alternative hypothesis for statistical analysis. An example of a null hypothesis from our coffee example is, “If you drink coffee before going to bed, it will have no impact on how long it takes to fall asleep.”
Hypothesis Examples to Help You Write a Hypothesis
The best way to learn how to write a hypothesis is to read example hypotheses. Below are a couple of example hypotheses.
Hypothesis Example 1: Smoking and Lung Cancer
A hypothesis explores the relationship between independent and dependent variables. Let’s say we are interested in the relationship between smoking habits and lung cancer. Our independent variable is smoking habits and our dependent variable is lung cancer.
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Next, we have to use our hypothesis to make a prediction about the relationship between smoking habits and lung cancer. Based on background knowledge we might guess that daily smoking increases the risk of lung cancer. This is our alternative hypothesis. The null hypothesis requires us to predict that there is no relationship between the variables.
Our null hypothesis is, “Daily smoking does not affect the risk of lung cancer.” Our alternative hypothesis is, “Daily smoking increases the risk of lung cancer.” Both hypotheses have an independent and dependent variable, both are testable, and both predict a relationship between the two variables.
Hypothesis Example 2: Vitamins and Hair Growth Rate
Say you work for a company that distributes vitamins. You think vitamins E and K help hair growth, but there is limited evidence about how these different vitamins impact hair growth. You decide to conduct a single experiment on how vitamins impact hair growth for scientific exploration.
You have a strong research question, “Does vitamin E or vitamin K make your hair grow faster?” Now we need to turn that into an experimental hypothesis. Our independent variable is what vitamins to take and our dependent variable is the hair growth rate. This is a complex hypothesis because we are testing two vitamins, two independent variables.
The null hypothesis is, “Neither vitamin E nor vitamin K impact hair growth rate.” One possible alternative hypothesis is, “Both vitamins E and K increase hair growth rate.” There are also a few other possible alternative hypotheses depending on what you think the relationship is between vitamin E and hair growth vs vitamin K and hair growth.
How to Use Hypothesis Examples to Write Your Own
The hypothesis examples we’ve discussed should give you a starting point for writing your own hypotheses. Use your research skills to develop a research question and then use our tips to rewrite it into a testable hypothesis with a simple prediction.
How to Write a Hypothesis FAQ
A hypothesis is a statement that describes a research question and predicts a relationship between variables. The same information can be posed as a question, but a true hypothesis is written as a statement. Hypotheses are often written as if-then statements.
A null hypothesis is a type of hypothesis that predicts that there is no relationship between your variables. For instance, if your research question is, “Is it important to integrate mental health education into schools?” Your null hypothesis is, “Implementation of mental health education in school will not affect students.
An alternative hypothesis means you expect that there is some relationship between variables. Let’s use the research question, “Is it important to integrate mental health education into schools?” An alternative hypothesis to that would be “Implementing mental health education in school programs will impact students.”
A good hypothesis is a simple statement of a research question that is testable and must include a dependent variable, an independent variable, and a prediction of the relationship between the two variables. There are also specific types of hypotheses such as a directional hypothesis, a non-directional hypothesis, or an associative hypothesis.
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