Standard Article

Statistical Power

  1. Kevin R. Murphy

Published Online: 30 JAN 2010

DOI: 10.1002/9780470479216.corpsy0944

Corsini Encyclopedia of Psychology

Corsini Encyclopedia of Psychology

How to Cite

Murphy, K. R. 2010. Statistical Power. Corsini Encyclopedia of Psychology. 1–2.

Author Information

  1. Pennsylvania State University

Publication History

  1. Published Online: 30 JAN 2010

Abstract

One of the most common statistical procedures in the behavioral and social sciences is testing the hypothesis that treatments or interventions have no effect, or that the correlation between two variables is equal to zero—that is, tests of the null hypothesis (H0). There are two ways to make errors when testing a null hypothesis: (1) Type I error, which consists of rejecting the null hypothesis when it is in fact true, and (2) Type II error, which consists of failing to reject the null hypothesis when it is in fact false. Statistical power is defined as 1 minus the conditional probability of making a Type II error. That is, power is the probability of rejecting the null hypothesis when it is in fact false.

Keywords:

  • power;
  • effect size;
  • sample size;
  • type II error