What is a Null Hypothesis?

Definition: A null hypothesis is a statistical assumption that suggests that two variables don’t affect each other in any way. It is a hypothesis that needs to be proven in order to be either accepted or rejected.

What Does Null Hypothesis Mean?

This hypothesis starts by assuming, in a negative sense, that a relation between the variables being studied doesn’t exist. In order to prove or disprove the hypothesis a test must be made. The most common intention of the researcher is to disprove the null hypothesis, but the result might also be that the null hypothesis is confirmed. Test results will define the accuracy of the statement. Null hypothesis are used in combination with alternative hypothesis.

The alternative hypothesis disagrees with the null one and the researcher will focus on disprove the null hypothesis in order to approve the alternative hypothesis. It doesn’t mean the alternative hypothesis is correct, but by discarding the new one the research process can continue until one of the hypotheses is absolutely confirmed.

Example

The Marketing Manager of a company called High Sound LLC is currently researching the relationship between two products that are sold together, a guitar and a guitar maintenance kit. The research project started when the owner of the company approached the Manager with a null hypothesis about the interaction between the sales of two different products.

The null hypothesis was: “There is no impact in the monthly number of guitar maintenance kits being sold if we sell more guitars”. After being addressed with this hypothesis the Marketing Manager formulated an alternative one that he would like to prove.

His alternative hypothesis was: “The number of guitar maintenance kits sold in a month increases when there’s an increase in the number of guitars sold in a month”. By testing the null hypothesis the Marketing Manager will be able to prove or disprove his own alternative hypothesis.

After conducting the test, the results showed that the null hypothesis was not correct; this meant that the alternative hypothesis became the accepted one.