Find statistical considerations for a study
where the outcome is a time to failure

Significance Level -- sided (default= .05, 2 sided).

Accrual interval Follow-up interval Median time to failure in group with smallest time to failure, in

Enter two of the following three values and the remaining value will be calculated.

  1. Power, usually .8 or .9.
  2. Total number of patients.
  3. Minimal detectable hazard ratio or ratio of median survival (>1)

Last Updated Sat May 3 22:56:39 EDT 2001
David A. Schoenfeld, Ph.D.,
With support from the Massachusetts General Hospital Mallinckrodt General Clinical Research Center, Research Resources Division, National Institutes of Health, General Clinical Research Center Program.


Schoenfeld D, Richter J. Nomograms for calculating the number of patients needed for a clinical trial with survival as an endpoint. Biometrics. 1982; 38:163-170.