Power and Sample Size Calculation for Non-Proportional Hazards

Performs power and sample size calculation for non-proportional hazards model using the Fleming-Harrington family of weighted log-rank tests. The sequentially calculated log-rank test score statistics are assumed to have independent increments as characterized in Anastasios A. Tsiatis (1982) . The mean and variance of log-rank test score statistics are calculated based on Edward Lakatos (1986) and Kaifeng Lu (2021) . The boundary crossing probabilities are calculated using the recursive integration algorithm described in Christopher Jennison and Bruce W. Turnbull (2000, ISBN:0849303168). The inverse normal combination method due to Lu Cui, H. M. James Hung, and Sue-Jane Wang (1999) is used in the simulation study to accommodate the information time not proportional to the total number of events for weighted log-rank tests.