Statistics Seminar

Abstract: A popular design choice in public health and implementation science research, stepped wedge cluster randomized trials (SW-CRTs) are a form of randomized trial whereby clusters are progressively transitioned from control to intervention, and the timing of transition is randomized for each cluster. An important task at the design stage is to ensure that the planned trial has sufficient power to observe a clinically meaningful effect size. While methods for determining study power have been well-developed for SW-CRTs with continuous and binary outcomes, limited methods for power calculation are available for SW-CRTs with censored time-to-event outcomes. In this talk, we propose a stratified marginal Cox model to account for secular trend in cross-sectional SW-CRTs, and derive an explicit expression of the robust sandwich variance that incorporates a definition of “Intracluster correlation” to facilitate power calculations and. I’ll also show how we developed power formulas based on both the Wald and robust score tests and compare them via simulation, particularly focusing on finite-sample scenarios common in pragmatic trial settings.