Encyclopedia of Psychology | Significance Level

A method to describe the reliability of test results.

When researchers measure a behavior, they often compare groups to determine whether they differ on that behavior. The ultimate goal is to determine whether the difference would occur if the measurements were administered a second time, or whether the difference is accidental and not likely to recur. The degree of reliability relates to the concept of significance level. The significance level refers to how likely it is that an error (that is, a wrong decision about whether the groups differ from one another) would be made. Psychologists generally accept a 5 percent error rate as reasonable. In order to decide whether differences are reliable, psychologists conduct statistical tests that provide a measure of confidence in their conclusions. This area of statistics is called inferential statistics because psychologists draw inferences, or conclusions,...