title: Consideration of covariates and stratification in sample size determination for survival time studies.
abstract: Sample size determination for survival time studies is discussed, taking into account stratification. We present formulas and tables which also apply in the case of multicenter clinical trials. In addition, the same method is used to estimate the sample size requirement when a covariate is grouped into strata. Simulation studies compare the results to covariate adjustment by the Cox proportional hazards model.
mesh_terms: D005500:Follow-Up Studies; D009026:Mortality; D013223:Statistics as Topic