Two calculators for two-group survival analysis.
Calculator 1: Number of events, given relative hazard.
Instructions: Enter parameters in the red cells. Answers will appear in blue below.
The standard normal deviate for α = Zα =
The standard normal deviate for β = Zβ =
A = (Zα+Zβ)2 =
B = (log(RH))2q0q1 =
Total events needed = A/B =
Calculator 2: Sample size, given number of events.
This calculator will calculate the number of subjects needed in each group to achieve the number of events calculated above.
q1 = 0.300
q0 = 0.700
RH = 0.667
Total events =
|N||Events||Cumulative Event Rate|
Reference: Schoenfeld DA. Sample-size formula for the proportional-hazards regression model. Biometrics 1983;39:499-503.