Fig. 1

Bias of the estimates of β₁ (calculated as β_estimate − β_true) for different scenarios under a multicenter randomized controlled trial study design (a–c) and an observational study design (d–f) based on 1000 simulations for each scenario. All scenarios used a β₁ of log(1.5), a control outcome rate of 15%, and an intracluster correlation coefficient of 0.08. GEE Generalized estimating equation, GLM-Bin Log-binomial regression model, GLMM Generalized linear mixed model