Objective: To evaluate how often sample size calculations and methods of statistical analysis are pre-specified or changed in randomised trials. Design: Retrospective cohort study. Data source: ...

The selection of suitable outcomes and sample size calculation are critical factors in the design of a randomised controlled trial (RCT). The goal of this study was to identify the range of ...

Cluster randomized trials in health care may involve three instead of two levels, for instance, in trials where different interventions to improve quality of care are compared. In such trials, the ...