The Power of Statistics in the Design of a Study

Abstract

An analysis of the power of the statistical methods used is very important in designing any research project or investigation. The major concepts regarding statistical power include the sample size of the study, the desired detectable effect size, the specified Type I error rate, and the sensitivities of statistical testing. The purpose of this article is then to explain the procedures a researcher should employ in order to make such statistical power explicit in the design of his or her study. Two empirical investigations are described in order to illustrate Type I and Type II error by examining sample size, statistical tests, measures, treatment effects, and variability within the subject groups of these two studies. Finally, some procedures for the consideration of statistical power in experimental design are suggested.