Fig. 2From: Optimal futility stopping boundaries for binary endpointsProbability of early termination under the alternative hypothesis \(p_a\) for \(p_a-p_0 = 0.15\), \(\alpha = 0.05\) and \(\beta = 0.2\). PET(\(p_a\)) corresponds to the probability of wrongly stopping for futility at the interim analysisBack to article page