
Number of patientsN_{0}


θ

d=2,p=0.2

d=8,p=0.5


0

160

184

0.1

204

226

0.2

252

274

0.3

296

320

0.4

340

366

0.5

380

422

 The simulation algorithm was applied to derive the number of individuals required for 80% power applying the robust twosided Wald test at a 5% significance level for different frailty variances θ and riskfree intervals of length d (weeks) following an event with probability p. Each result was derived from 10000 simulation runs.