At kth interim look k = 1 k = 2 k = 3 total Type I error Empirical of S(t) 0.0028 0.0047 0.0422 0.0496 Nominal 0.0024 0.0046 0.0436 0.0506 Power         Empirical of S(t) 0.171 0.2994 0.3886 0.8389  Nominal 0.1204 0.2533 0.4257 0.7994 Probability of stopping under null Empirical of S(t) 0.2574 0.3907 0.3519 1 Nominal 0.2626 0.3916 0.346 1 Probability of stopping under alternative Empirical of S(t) 0.1756 0.315 0.5094 1  Nominal 0.1315 0.28 0.5885 1

Table 3: Operating characteristics of the three-stage SCPRT design for test statistic S(t)based on 100,000 simulation runs under the Weibull distribution with uniform censoring distribution on [tf ,ta+ tf], and nominal type I error of 0.05 and power 80% for the example in Section 6.