How to Write a Hypothesis: Examples, Types, and Research Tips

"Students who sleep fewer than six hours perform worse on memory tasks than those who sleep eight or more." 

The statement above is a prime example of a hypothesis, a specific, testable prediction about the expected relationship between two or more variables that is proposed before conducting research, and designed to be confirmed or disproved by evidence. There are some rules you need to follow to write a hypothesis. For one, it should be testable. Also, it should present specific ideas. 

In this article, we cover everything you need to know about what a hypothesis is, its different types, how to write one for your research, and give you examples along the way.

What Is a Hypothesis?

A hypothesis is an if/then statement about the relationship between two or more variables. It is definitely not just a guess. Neither is it a question. A hypothesis is very specific, and it always predicts what will happen before any data is collected. The research then either supports it or does not, and both outcomes are useful. Without a hypothesis, your research will lack direction. To create a hypothesis statement, you should pull your thoughts together and identify what you want to look at.

Hypothesis Characteristics

If hypotheses have anything in common, it is these few characteristics. Without these qualities, your hypothesis can do more harm than good later on in your research.

• Testable: Able to be proven right or wrong by collecting data.
• Specific: Clearly states your variables and the predicted relationship.
• Falsifiable: There is a possibility to show that your hypothesis is false.
• Grounded: Based on what is already known or has been studied in the past, not a guess.
• Clear: Free of ambiguous language.

Hypothesis Sources

A hypothesis doesn't just magically appear in your mind. It originates from somewhere. The following list includes places you can look to help generate ideas. You'll find that searching in these places is far less aggravating than hoping for ideas to come to you.

• Previous research: Other research can suggest holes that need to be filled or questions that need to be answered.
• Observation: Something you notice from everyday life that you want to know why it happens
• Theory: Previously established theories make predictions that you can test
• Replication: Conducting a study that has been done before, but with a new population
• Practical problems: A problem that occurs in a field that leads you to believe there is a relationship between two variables

Analytical writing skills also apply to history assignments. Our guide on how to write a DBQ explains how to structure evidence-based arguments.

Types of Hypothesis

There are several different types of scientific hypothesis, depending on what you intend to achieve with your research and what sort of claim you are making. It can help to determine which type you’re utilizing to ensure your study question and methods remain aligned throughout the research process.

Null Hypothesis: States that there is no relationship between the variables being studied. It is the default position that research either confirms or rejects. Null hypothesis examples: "There is no significant difference in exam performance between students who sleep six hours and those who sleep eight." /  "There is no significant difference in reported stress levels between employees who exercise daily and those who do not."

Alternative Hypothesis: The direct opposite of the null. It proposes that a relationship does exist and is usually what the researcher actually expects to find. Alternative hypothesis example: "Students who sleep eight hours perform significantly better on exams than those who sleep six."

Simple Research Hypothesis: Predicts a relationship between one independent variable and one dependent variable. Straightforward and easy to test. Example: "Increased daily exercise reduces reported stress levels in university students."

Complex Hypothesis: Involves two or more variables on either side of the relationship. More difficult to test but often more realistic in reflecting how things actually work. Example: "Increased daily exercise and improved sleep quality together reduce stress levels and improve academic performance in university students."

Directional Hypothesis: Specifies not just that a relationship exists but the direction it will take, whether one variable will increase or decrease relative to another. Example: "Students who revise using spaced repetition will score higher on retention tests than those who use massed practice."

Non-directional Hypothesis: Predicts that a relationship exists between variables without specifying which direction it will go. Used when existing research does not clearly point one way. Example: "There will be a significant difference in stress levels between students who exercise daily and those who do not."

Hypothesis Format

Most hypotheses are written in the form of an “If... then…” statement. There is a reason for that. Writing a hypothesis this way forces you to write the cause before the effect. It helps you keep your prediction specific and keeps the relationship between your variables clear.

"If"[Independent Variable], "then"[dependent variable].

"If university students limit their time on social media to less than an hour a day," then "their self-reported anxiety levels will lower over a four week time period."

You will not always have to write your hypothesis in this format. There are times when your hypothesis will more precisely show the relationship between variables if you just state it as a fact. However, if you are a student just learning how to write them, this is a good formula to start with because it forces you to make your prediction specific and testable, starting with your first draft.

How to Write a Hypothesis?

Writing a good hypothesis is a process rather than a single decision. It starts with a question and ends with a specific, testable statement that gives the research a clear direction. Five steps tend to structure this well.

Step 1: Begin With a Question

Before creating a good hypothesis, you need something to base it on – ideally, a question you’d like to find the answer to. Your question should be narrow enough that you can answer with data, but broad enough that there isn’t already an obvious answer.

Example question: Does the amount of sleep a student gets impact their ability to complete memory tasks?

Step 2: Know the Literature

Before you try to make a new discovery, you should see what has already been discovered on your topic. Knowing the literature shows you what is already known about your topic, what direction the evidence is pointing, and helps you see how your study will add to what is already known. A literature-based hypothesis will be exponentially stronger than one based purely on intuition.

Example: If you’re looking at the relationship between sleep and memory recall, and every study you read finds that sleep deprivation negatively affects cognition, your hypothesis should probably follow that direction rather than being the opposite without solid justification.

Step 3: Know Your Variables

Ideally, you’ll know your independent variable and dependent variable before you even begin to write your hypothesis. This is where most students stumble. If you are having trouble, skip ahead to this mini- guide on identifying variables.

Independent Variable (IV): The variable that you are changing. Often thought of as the cause side of the relationship.

Dependent Variable (DV): The variable that you are measuring. Often thought of as the effect side of the relationship.

Example: If you are testing how much sleep someone gets and their performance on a memory task, sleep would be your IV because that is what you are changing. Memory task performance is your DV because that is what you measure.

Quick test: Ask yourself, “what am I changing?” and “what am I measuring?” Those two answers are your IV and DV.

Step 4: Start Simple, Then Make It Formal

Many students will immediately think of the formal version of their hypothesis. Don’t. First, write your hypothesis in simple terms. Here is how to state a hypothesis in correct logic:

Simple version: More sleep leads to better memory.

This is acceptable, but too broad to be tested. How much sleep is more? What kind of memory task? What population are we studying?

Formal Version: University students who sleep eight or more hours per night will perform better on short-term recall tasks than students who sleep less than six hours per night.

Simple! Now your hypothesis has identified the population that you will study, the variables, the direction of the relationship, and how you will measure that relationship. The more specific you can be, the easier it will be to test.

Step 5: Use If…Then format

Take your formalized hypothesis and compare it to the If….Then format. This helps confirm that the relationship between your variables is clear.

“If university students sleep eight or more hours per night, then their short term recall ability will be better than students that sleep fewer than six hours per night.”

If your hypothesis reads nicely in this format, you’re ready to start testing. If it doesn’t sound right or is too vague, go back and revisit either your variable identification or the direction of your claim and restate your hypothesis.

If you are still choosing a subject for your paper, explore these informative essay topics for research and writing ideas.

Hypothesis Examples

A good hypothesis example is narrow enough that you can easily see how you would test it. It names the population, it clearly identifies the variables, states the direction of the predicted relationship, and is worded specifically enough that someone else could go off and design a study to test your hypothesis. "Stress affects performance" isn't good enough because you don't know who, how, or in what direction. Here are some effective examples:

Hypothesis vs. Prediction

Students tend to confuse these two quite frequently, and to be honest, it’s understandable why. Both a hypothesis and prediction are statements that describe what you think will happen before you begin your research or experiment. The key difference is the complexity behind them. Here's how a hypothesis is different from a prediction.

• A hypothesis is an educated statement based on prior theory/research. It should be testable and explain how or why two variables are related. The purpose of a hypothesis is to make a general claim about how multiple pieces of data relate and fit into the current scientific understanding of a topic.
• A prediction is much less complex. It simply states what you think will happen. It doesn’t have to connect to previous research or explain why you think one result is more likely than another. A prediction also usually only applies to one specific situation.

To put it more simply, you can make many predictions from one hypothesis. But a prediction is only one possible outcome of one possible scenario.

Hypothesis: Students who practice retrieval when revising will remember more information after two weeks compared to students who read their notes, due to previous research done on retrieval practice.

Prediction: I predict that the students who used Quizlet will get a higher grade on Friday’s exam.

The hypothesis includes information on why we expect retrieval practice to work. The prediction just states what will happen in one specific instance. You’ll use both in a research project. However, they are not interchangeable in an academic setting.

To Wrap Up

Crafting a good hypothesis requires more forethought than most students initially give it. However, after determining your variables and having a research question specific enough, the statement will typically come fairly quickly. Nail that down, and the rest of your study will have something to build towards. It's worth it to take the time you need to achieve clarity.

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