Fig. 1From: Extension of a conditional performance score for sample size recalculation rules to the setting of binary endpointsGlobal power and mean sample size for the considered recalculation rules for binary endpoints in the main simulation. The red dashed line represents the sample size and power for a fixed design with a target power of 80% for an assumed \(\lambda =0.3\). The proportion in the control group is set to \(p_{C}=0.3\) and the first stage sample size is set to \(n_{1}=50\). The global significance level \(\alpha = 0.025\), efficacy stopping boundaries were chosen according to Pocock [15] and the binding futility stopping bound is set to \(\alpha _{0}=0.5\). The maximum sample size is set to \(n_{max} = 200\). OCP: Observed conditional power approach; restrOCP: Restricted observed conditional power approach; Promising: Promising zone approach; OptFunc: Optimization function approach; classicGS: group sequential approachBack to article page