Access Type

Open Access Dissertation

Date of Award

January 2021

Degree Type


Degree Name



Education Evaluation and Research

First Advisor

Shlomo S. Sawilowsky

Second Advisor

Stephen B. Hillman


A REVIEW OF SAMPLE SIZE AND DESIGN EFFICACY IN CROSSOVER DESIGN IN PEER-REVIEWED PSYCHOLOGY RESEARCHby KYLE C. MOXLEY November 2021 Advisor: Dr. Shlomo S. Sawilowsky Major: Education Evaluation and Research Degree: Doctor of Philosophy The present study seeks to investigate the efficacy of crossover research designs, and the application of crossover designs, in the field of behavioral sciences. Under ideal conditions, crossover designs are assumed to be more efficacious than parallel studies in that participants are given both treatments. However, the presence of carryover effects from treatments may influence outcomes (Jones & Kenward, 2014). To prevent carryover effects, researchers frequently implement washout periods to bring participants back to baseline. The present study seeks to examine whether the amount of time utilized in washout periods influences effect sizes in published psychology articles, and how safeguards against carryover are implemented. The present study uses a systematic review to examine crossover designs in peer-reviewed journals in psychological research over a ten-year period. Findings suggest the amount of time utilized in washout periods has an impact on effect sizes in published psychology articles. The current thesis also looks at the frequency of crossover design in the field of psychology, and the rigor around implementing washout and the carryover effect.