Null Hypothesis Definition and Examples

What Is the Null Hypothesis?

A hypothesis is a prediction based on observations. The null hypothesis predicts no difference from an experimental variable or between two populations.
A hypothesis is a prediction based on observations. The null hypothesis predicts no difference from an experimental variable or between two populations. PM Images, Getty Images

Null Hypothesis Definition

The null hypothesis is the proposition that implies no effect or no relationship between phenomena or populations. Any observed difference would be due to sampling error (random chance) or experimental error. The null hypothesis is popular because it can be tested and found to be false, which then implies there is a relationship between the observed data.

The alternate hypothesis, HA or H1, proposes observations are influenced by a non-random factor.

In an experiment, the alternate hypothesis suggests the experimental or independent variable has an effect on the dependent variable.

Also Known As: H0, no-difference hypothesis

Null Hypothesis Examples

"Hyperactivity is unrelated to eating sugar." is an example of a null hypothesis. If the hypothesis is tested and found to be false, using statistics, then a connection between hyperactivity and sugar ingestion may be indicated. A significance test is the most common statistical test used to establish confidence in a null hypothesis.

Another example of a null hypothesis would be, "Plant growth rate is unaffected by the presence of cadmium in the soil." A researcher could test the hypothesis by measuring the rate of plant growth of plants grown in a medium lacking cadmium compared with the rate of growth of plants grown in a medium containing different amounts of cadmium. Disproving the null hypothesis would set the groundwork for further research into the effects of different concentrations of the element in soil.

Format
mla apa chicago
Your Citation
Helmenstine, Anne Marie, Ph.D. "Null Hypothesis Definition and Examples." ThoughtCo, Jul. 24, 2016, thoughtco.com/definition-of-null-hypothesis-and-examples-605436. Helmenstine, Anne Marie, Ph.D. (2016, July 24). Null Hypothesis Definition and Examples. Retrieved from https://www.thoughtco.com/definition-of-null-hypothesis-and-examples-605436 Helmenstine, Anne Marie, Ph.D. "Null Hypothesis Definition and Examples." ThoughtCo. https://www.thoughtco.com/definition-of-null-hypothesis-and-examples-605436 (accessed January 23, 2018).