Operating characteristics for 1,000 simulated trials under three scenarios for Example 2: 3 stages, 10 stages, and a random number of stages, all with random cohort sizes. Subpanels: (A) Type I error rates, (B) Power for detecting a response rate of 80%, (C) Probability of early termination if the true response rate is 60% and (D) Expected sample size if the true response rate is 60%. Line types:……Simon’s minimax two-stage design, -----Predictive probability design, monitoring every patient, -·-·- Predictive probability design, monitoring every 5 patients.