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Sample size comparison between Z-test in a fixed design and the adjusted test in a two-stage design with internal pilot (with n1 = 30, 15 respectively). The total sample size (per arm) is calculated to achieve 80% power under a 20-percentage-point effect size at 5% significance (one-sided).
| Placebo rate | 10% | 15% | 20% | 25% | 30% | 35% | 40% |
|---|---|---|---|---|---|---|---|
| Z-test | 49 | 57 | 64 | 70 | 74 | 76 | 77 |
| Adjusted test (n1 = 30) | 50 | 58 | 66 | 71 | 75 | 78 | 79 |
| Adjusted test (n1 = 15) | 51 | 63 | 72 | 79 | 85 | 88 | 89 |
