May 1, 2024
IMPACT Design and Statistics Core members Xueqi Wang, PhD, Keith Goldfeld, DrPH, MS, MPA, Monica Taljaard, PhD, and Fan Li, PhD, author new article considering the two-treatment two-period cluster randomized crossover design under either a cross-sectional or closed-cohort sampling scheme, where it is of interest to detect the heterogeneity of treatment effect via an interaction test. Formulas address unequal cluster sizes and allow researchers to analytically assess the impact of unequal cluster sizes on the power of the interaction test in cluster randomized crossover designs. Simulations were conducted to confirm the accuracy of the proposed methods, and illustrate their application in two real cluster randomized crossover trials.