In hypothesis testing, which hypothesis is usually tested first?

In hypothesis testing, the null hypothesis is typically tested first because it serves as the baseline or default position. The null hypothesis represents a statement of no effect or no difference, and it is what researchers seek to challenge or refute with their data. The aim of a hypothesis test is to determine whether the evidence gathered in a study is strong enough to reject the null hypothesis in favor of the alternative hypothesis, which posits that there is an effect or a difference.

By initially testing the null hypothesis, researchers can systematically establish a framework for assessing the strength of evidence against it and subsequently evaluate whether support exists for the alternative hypothesis. This approach also helps control for Type I errors, where researchers might conclude that an effect exists when it does not.

Understanding this foundational step is crucial, as it provides the basis for making inferences about a population based on sample data. Hence, the initial focus on the null hypothesis is a fundamental principle in statistical hypothesis testing.