ABSTRACT
Within-subjects (also known as repeated measures) designs focus on approaches involving measurement of the same participants at multiple levels of a factor (also known as independent variable). Often these designs involve measurement over two or more time periods. This chapter examines power for one and two factor within subject Analysis of Variance (ANOVA) designs and trend analyses using both classic ANOVA approaches and linear mixed models (LMM). The chapter discusses and demonstrates issues with violation of the sphericity assumption. Examples focus on calculations and analyses using univariate and LMM, and present R functions from the pwr2ppl package for primary analyses, sphericity-adjusted tests, and trends.
