What Is a Hypothesis?

A hypothesis is a research-based prediction of an outcome involving at least two variables in an experiment or test. For a prediction to be considered a hypothesis, it must be testable. In other words, you need to be able to manipulate the two variables to prove your prediction. It must also be falsifiable. This means there is more than one possible outcome, and a chance that your prediction will be proved false.

Part of a Hypothesis

A hypothesis has three components, which are also requirements for it to be considered a hypothesis: 

A.      Independent variable: The independent variable is the one that is expected to cause a change at the end of the experiment.

B.      Dependent variable: The dependent variable is the one that is expected to be changed by the independent variable at the end of the experiment.

C.      Reasoning based on research: The reasoning part of the hypothesis should include an explanation, based on facts and research.

Using these components, a hypothesis follows the “If A, then B, because C” format, where “A” is the cause, “B” is the effect, and “C” is the reason. The following “fill-in-the-blank” structure may help you to better understand the segments of a hypothesis:

If _______ (state “A” how it will react with “B”), then _______ (state “B” and how it will change), because __________(provide “C”).

How to Write a Hypothesis

To write your hypothesis, follow these basic steps:

1)      Determine what elements (independent and dependent variables) you would like to include in your experiment.

2)      Ask a question about what would happen if these variables were to interact.

3)      Use your prior knowledge of the variables, and conduct research to form an educated prediction of what the outcome will be.

4)      Develop your hypothesis, which should include an answer to the question you asked in step 2.

Hypothesis Examples

Here is an example of a scientific experiment, along with a hypothesis about it:

You have about 2 cups of strawberries to be stored in a mason jar. You also have a mixture of water and distilled vinegar to wash the berries with. You want to determine if the water + vinegar mixture will preserve the better for longer than water alone.

·         Independent variable: Distilled vinegar

·         Dependent variable: Strawberries

·         Reasoning: Prior knowledge of distilled vinegar acting as a preservative, trials, etc.

So the question is: Does washing strawberries in distilled vinegar and water keep them fresh for longer than soaking them in water alone? After conducting some research and testing both solutions (one with vinegar and one without), you hypothesize that:

If you rinse strawberries soak them in a water/distilled vinegar mixture for 10 minutes, then the strawberries will be preserved for three more days than if you didn’t use vinegar, because of the vinegar’s preserving acetic acid content.

Remember, a hypothesis must be falsifiable. Therefore, it should be possible that the vinegar will not keep the strawberries fresh for longer than water alone.

Types of Hypotheses

Some of the most common types of hypothesis include:

·         Simple: Combines only independent variable and one dependent variable

·         Complex: Involves at least two dependent variables and at least two independent variables

·         Directional: Predicts a positive or negative relationship between the dependent and independent variable

·         Non-directional: Predicts a relationship between two variables without specifying if it’s positive or negative

·         Null: Proposes that one variable has little or no effect on the other  

·         Alternative: Claims that a null hypothesis is false

Scientific Hypothesis vs. Research Hypothesis

The variables involved in a standard classroom or laboratory science experiment typically involve a solid, liquid, or gas. Such an experiment might involve a food and a chemical. However, in psychology and other forms of research, a hypothesis can also involve a much longer list of variables. This list includes people, specific settings, actions, situations, etc. For example, you may want to determine if a person will respond differently to a certain stimulus if they are first exposed to the responses of others.