Research Design and Statistical Consulting
George M. Diekhoff, Ph.D.

Using G*Power to Estimate Sample Size or Statistical Power for One-Way Within-Subjects (Repeated Measures) MANOVA

G* Power does not include an app to do power analysis for this very popular statistical procedure. It’s misleading, because under G*Power’s drop down list for F tests it says that it can run calculations for “MANOVA: Repeated Measures.” This procedure involves measuring multiple outcome variables (DVs)on the same sample multiple times (i.e., time1, time2, time3, etc.). One of the creators of G*Power confirmed that this app is NOT intended for use with one-way within-subjects MANOVA, but the app is actually intended to provide power analysis for those who want to use MANOVA to analyze univariate repeated-measures data–which is sometimes done when the sphericity assumption is not met in the univariate procedure.