Table 2 Four test settings (a-d) for futility and efficacy stopping with cumulative probabilities under the null hypothesis, \(\alpha ^{*}_{l}\) and \(\alpha ^{*}_{u}\) for one, two and three interim analyses
Interims | \(\alpha ^{*}_{l}\) | \(\alpha ^{*}_{u}\) | |||
|---|---|---|---|---|---|
(a) | (b) | (c) | (d) | ||
One interim analyses | |||||
 1 | 0.160 | 0.320 | 0.480 | 0.640 | 0.005 |
 End | 0.975 | 0.975 | 0.975 | 0.975 | 0.025 |
Two interim analyses | |||||
 1 | 0.080 | 0.160 | 0.240 | 0.320 | 0.001 |
 2 | 0.160 | 0.320 | 0.480 | 0.640 | 0.010 |
 End | 0.975 | 0.975 | 0.975 | 0.975 | 0.025 |
Three interim analysis | |||||
 1 | 0.080 | 0.160 | 0.240 | 0.320 | 0.001 |
 2 | 0.160 | 0.320 | 0.480 | 0.640 | 0.005 |
 3 | 0.240 | 0.480 | 0.720 | 0.960 | 0.010 |
 End | 0.975 | 0.975 | 0.975 | 0.975 | 0.025 |