Power analysis in research

Abstract

Statistical power is a measure of the likelihood that a researcher will find statistical significance in a sample if the effect exists in the full population. Power is a function of three primary factors and one secondary factor: sample size, effect size, significance level, and the power of the statistic used. The most common reason to conduct a power analysis is to determine the sample size needed for a particular study. However, power analysis may also be used after a study has been completed to determine if the reason an effect was not significant was insufficient power. Generally, however, post hoc power analysis is not suggested; that work should be done prior to beginning a study. The influence of effect size, significance, sample size, and the power of the statistic are explored.