What is a Type II Error?

A Type II error occurs when the null hypothesis is accepted even though it is false. This means that the test fails to identify a true effect or difference that exists in the population. In practical terms, if a study is designed to detect the presence of an association or effect between variables, a Type II error implies that the study has concluded that there is no association, while in fact, there is one.

This is an important concept in hypothesis testing. When performing statistical analyses, researchers aim to minimize both Type I errors (rejecting a true null hypothesis) and Type II errors. The ability to detect an effect when one exists—the power of a test—plays a crucial role in the likelihood of making a Type II error. Factors influencing this include sample size, effect size, and significance level.

Understanding the implications of a Type II error is vital for interpreting research findings and making informed decisions based on statistical data.