A hypothesis is a prediction of the outcome of a test. It forms the basis for designing an experiment in the scientific method. A good hypothesis is testable, meaning it makes a prediction you can check with observation or testing. Here are different hypothesis examples.

**Null Hypothesis Examples**

The null hypothesis (H_{0}) is also known as the zero-difference or no-difference hypothesis. It predicts that changing one variable (independent variable) will have no effect on the variable being measured (dependent variable).

- Plant growth is unaffected by temperature.
- If you increase temperature, then solubility of salt will increase.
- Incidence of skin cancer is unrelated to ultraviolet light exposure.
- All brands of light bulb last equally long.
- Cats have no preference for the color of cat food.
- All daisies have the same number of petals.

Sometimes the null hypothesis is used to show there is a correlation between two variables. For example, if you suspect plant growth is affected by temperature, you could state the null hypothesis. Why would you do this, rather than say “If you change temperature, plant growth will be affected”? The answer is because it’s easier to apply a statistical test to show, with a high level of confidence, a null hypothesis is correct or incorrect.

**Research Hypothesis Examples**

A research hypothesis (H_{1}) is a type of hypothesis used to design an experiment. This type of hypothesis is often written as an if-then statement because it’s easy to identify the independent and dependent variables and see how one affects the other. If-then statements are used to explore cause and effect. In other cases, the hypothesis is stated to show a correlation between two variables. Here are some research hypothesis examples:

- If you leave the lights on, then it will take longer for people to fall asleep.
- If you refrigerate apples, they will last longer before going bad.
- If you keep the curtains closed, then less electricity will be used to heat or cool the house (electric bill will be lower).
- If you leave a bucket of water uncovered, then it will evaporate more quickly.
- Goldfish lose their color if they are not exposed to light.
- Workers who take vacations are more productive than those who never take time off.

**Is It Okay To Disprove a Hypothesis?**

Yes! You may even choose to write your hypothesis in such a way that it can be disproved because it’s easier to prove a statement is wrong than to prove it is right. In other cases, if your prediction is incorrect, that doesn’t mean the science is bad. Revising a hypothesis is common. It demonstrates you learned something you did not know before you conducted the experiment.

Test Yourself with a Scientific Method Quiz