Simulation study scenarios
deaths
EVENTS, RECRUITMENT
We use simulations to compare the properties of the new UMVCUE, the naive estimator and the existing bias adjusted estimators by Brückner et al that are described in Section The simulation study is based on the fifth selection rule in Table Sample sizes in simulations are such that, if it was a single‐stage trial and the true hazard ratio (HR) is 0.8, the combined stage 1 and stage 2 number of deaths from the control and the selected experimental treatment correspond to power of 80%. For 80% power, 632 deaths (rounded up to an even number) are required. We fixed deaths from patients recruited in stage 2, that is stage 2 patients, to be 316.Recalling that we take the shape parameter Assuming a uniform recruitment rate of 1 patient per day in stage 2, for the assumed hazard functions when HR is 0.8, we expect 316 events from stage 2 patients to be observed after 2 years. Therefore we fixed to follow the stage 1 patients from the control and selected experimental treatment without events at the interim analysis to be followed for 1 year post interim analysis.For each scenario, we simulated 100 000 trials and for each trial, we computed the naive estimate and four bias ajusted estimates corresponding to estimators in Sections 