How to write a Hypothesis

A complete Guide to how to write a Hypothesis for students and teachers.

Frequently, when we hear the word ‘hypothesis’ we immediately think of an investigation in the form of a science experiment. This is not surprising, as science is the subject area where we are usually first introduced to the term.

However, the term hypothesis also applies to investigations and research in many diverse areas and branches of learning. We can find hypotheses at work in areas as wide-ranging as history, psychology, technology, engineering, literature, design, and economics.

With such a vast array of uses, hypothesis writing is an essential skill for our students to develop.

What Is a Hypothesis?

how to write a hypothesis | Hypothesis definition | HOW TO WRITE A HYPOTHESIS | literacyideas.com
Hypothesis Definition

A hypothesis is a proposed or predicted answer to a question. The purpose of writing a hypothesis is to follow it up by testing that answer. This test can take the form of an investigation, experiment, or writing a research paper that will ideally prove or disprove the hypothesis’s prediction.

Despite this element of the unknown, a hypothesis is not the same thing as a guess. Though the hypothesis writer typically has some uncertainty, the creation of the hypothesis is generally based on some background knowledge and research of the topic. The writer believes in the likelihood of a specific outcome, but further investigation will be required to validate or falsify the claim made in their hypothesis.

In this regard, a hypothesis is more along the lines of an ‘educated guess’ that has been based on observation and/or background knowledge.

A hypothesis should:

  • Make a prediction
  • Provide reasons for that prediction
  • Specifies a relationship between two or more variables
  • Be testable
  • Be falsifiable
  • Be expressed simply and concisely
  • Serves as the starting point for an investigation, an experiment, or another form of testing

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Hypothesis Examples

If students listen to classical music while studying, then they will retain more information.

Mold growth is affected by the level of moisture in the air.

Students who sleep for longer at night retain more information at school.

Employees who work more than 40 hours per week show higher instances of clinical depression.

Time spent on social media is negatively correlated to the length of the average attention span.

People who spend time exercising regularly are less likely to develop a cardiovascular illness.

If people are shorter, then they are more likely to live longer.

What are Variables in a Hypothesis?

Variables are an essential aspect of any hypothesis. But, what exactly do we mean by this term?

Variables are changeable factors or characteristics that may affect the outcome of an investigation. Things like age, weight, the height of participants, length of time, the difficulty of reading material, etc., could all be classed as variables.

Usually, an investigation or experiment will focus on how different variables affect each other. So, it is vital to define the variables clearly if you are to measure the effect they have on each other accurately.

There are three main types of variables to consider in a hypothesis. These are:

  • Independent Variables
  • Dependent Variables

The Independent Variable

The independent variable is unaffected by any of the other variables in the hypothesis. We can think of the independent variable as the assumed cause.

The Dependent Variable

The dependent variable is affected by the other variables in the hypothesis. It is what is being tested or measured. We can think of the dependent variable as the assumed effect.

For example, if we investigate the correlation between test scores across different age groups, the age groups will be the independent variable, and the test scores would be the dependent variable.

Student Challenge

First, organize students into small working groups of four or five. Then, set each group the task of collecting a list of hypotheses. They can find these through searching on the Internet or finding examples in textbooks. When students have gathered together a suitable list of hypotheses, have them identify the independent and dependent variables in each case. They can underline each of these in different colors.

It may be helpful for students to examine each hypothesis to identify the ‘cause’ elements and the ‘effect’ elements. When students have finished, they can present their findings to the class as a whole.

Now we have a grasp of what variables are, let’s take a look at how they work in the various types of hypotheses.

Types of Hypotheses

There are many different types of hypotheses, and it is helpful to know the most common of these if the student is to select the most suitable tool for their specific job.

The most frequently used types of hypotheses are:

  • The Simple Hypothesis
  • The Complex Hypothesis
  • The Empirical Hypothesis
  • The Null Hypothesis
  • The Directional Hypothesis
  • The Non-Directional Hypothesis

The Simple Hypothesis

This straightforward hypothesis type predicts the relationship between an independent and dependent variable.

Example: Eating too much sugar causes weight gain.

The Complex Hypothesis

This type of hypothesis is based on the relationship between multiple independent and/or dependent variables.

Example: Eating too much sugar causes weight gain and poor cardiovascular health.

The Empirical Hypothesis

Also called a working hypothesis, an empirical hypothesis is put to the test through observation and experimentation. An empirical hypothesis is produced through investigation and trial and error. As a result, the empirical hypothesis may change its independent variables in the process.

Example: Exposure to sunlight helps lettuces grow faster.

The Null Hypothesis

This hypothesis states that there is no significant or meaningful relationship between specific variables.

Example: Exposure to sunlight does not affect the rate of a plant’s growth.

The Directional Hypothesis

This type of hypothesis predicts the direction of an effect between variables, i.e., positive or negative.

Example: A high-quality education will result in a greater number of career opportunities.

The Non-Directional Hypothesis

Similar to the directional hypothesis, this type of hypothesis predicts the nature of the effect but not the direction that effect will go in.

Example: A high-quality education will affect the number of available career opportunities.

How to Write a Hypothesis

  1. Ask a Question

The starting point for any hypothesis is asking a question. This is often called the research question. The research question is the student’s jumping-off point to developing their hypothesis. This question should be specific and answerable. The hypothesis will be the point where the research question is transformed into a declarative statement.

Student Challenge:

Set your students the task of coming up with an investigation-worthy question on a topic that interests them. This activity works particularly well for groups.

Ideally, the questions the students develop should be relational, i.e., it should look at how two or more variables relate to each other as described above. For example, What is the effect of sunlight on the growth rate of lettuce?

  1. Research the Question

The research is an essential part of the process of developing a hypothesis. Students will need to examine the ideas and studies that are out there on the topic already. By examining the literature already out there on their topic, they can begin to refine their questions on the subject and begin to form predictions based on their studies.

Remember, a hypothesis can be defined as an ‘educated’ guess. This is the part of the process where the student educates themself on the subject before making their ‘guess.’

Student Challenge:

Students search for existing information and theories on their topic on the Internet or in the library. They should take notes where necessary and begin to form an assumption or prediction based on their reading and research that they can investigate further.

  1. Define Your Variables

By now, your students should be ready to form their preliminary hypotheses. To do this, they should first focus on defining their independent and dependent variables. Now may be a good opportunity to remind students that the independent variables are the only variables that they have complete control over, while dependent variables are what is tested or measured.

Student Challenge:

Working with a talking partner, can students identify which of their partner’s variables are independent and dependent variables? If not, then one partner will need to revisit the definitions for the two types of variables as outlined earlier.

  1. Develop Your Preliminary Hypotheses

With variables defined, students can now work on a draft of their hypothesis. To do this, they can begin by examining their variables and the available data and then making a statement about the relationship between these variables. Students will need to brainstorm and reflect on what they expect to happen in their investigation before making a prediction upon which to base their hypothesis. It’s worth noting, too, that hypotheses are typically, though not exclusively, written in the present tense.

Student Challenge:

Students revisit the different types of hypotheses described earlier in this article. Students select three different types of hypotheses and frame their preliminary hypotheses according to each of these criteria. Which works best? Which type is the least suitable for the student’s hypothesis?

  1. Finalize the Phrasing

By now, students will have made a decision on which type of hypothesis suits their needs best, and it will now be time to finalize the wording of their hypotheses. There are various ways that students can choose to frame their hypothesis, but below, we will examine the three most common ways.

The If/Then Phrasing

This is the most common type of hypothesis and perhaps the easiest to write for students. It follows a simple ‘If x, then y’ formula that makes a prediction that forms the basis of a subsequent investigation.

E.g.,

If I eat more calories, then I will gain weight.

Correlation Phrasing

Another way to phrase a hypothesis is to focus on the correlation between the variables. This typically takes the form of a statement that defines that relationship positively or negatively.

E.g.,

The more calories that are eaten beyond the daily recommended requirements, the greater the weight gain will be.

Comparison Phrasing

This form of phrasing is useful when comparing two groups and focuses on the differences that the investigation is expected to reveal between those two groups.

E.g.,

Those who eat more calories will gain more weight than those who eat fewer calories.

Student Challenge:

Organize students into smaller groups and task them with presenting their hypotheses to each other. Students can then provide feedback before the final wording of each hypothesis is finalized.

Questions to ask during this process include:

  • What tense is the hypothesis written in?
  • Does the hypothesis contain both independent and dependent variables?
  • Is the hypothesis framed using the if/then, correlation, or comparison framework (or other similar suitable structure)?
  • Is the hypothesis worded clearly and concisely?
  • Does the hypothesis make a prediction?
  • Is the prediction specific?
  • Is the hypothesis testable?
  1. Gather Data to Support/Disprove Your Hypothesis

If the purpose of a hypothesis is to provide a reason to pursue an investigation, then the student will need to gather related information together to fuel that investigation.

While, by definition, a hypothesis leans towards a specific outcome, the student shouldn’t worry if their investigations or experiments ultimately disprove their hypothesis. The hypothesis is the starting point; the destination is not preordained. This is the very essence of the scientific method. Students should trust the results of their investigation to speak for themselves. Either way, the outcome is valuable information.

In Conclusion

Perhaps due to their short length, learning how to create a well-written hypothesis is not typically afforded much time in the curriculum.

However, though they are brief in length, they are complex enough to warrant focused learning and practice in class, particularly given their importance across many curriculum areas.

Learning how to write a hypothesis works well as a standalone writing skill. It can also form part of a more comprehensive academic or scientific writing study that focuses on how to write a research question, develop a theory, etc.

As with any text type, practice improves performance. By following the processes outlined above, students will be well on their way to writing their own hypotheses competently in no time.


The content for this page has been written by Shane Mac Donnchaidh.  A former principal of an international school and university English lecturer with 15 years of teaching and administration experience. Shane’s latest Book the Complete Guide to Nonfiction Writing can be found here.  Editing and support for this article have been provided by the literacyideas team.