Fig. 1
From: Adaptive designs in critical care trials: a simulation study
Critical value boundaries of three approaches with four interim looks and one final look. The solid lines represent the efficacy boundaries and the dashed lines represent the futility boundaries for the three group-sequential designs (red: Haybittle-Peto, brown: Hwang-Shih-DeCani, green: O’Brien-Fleming). Orange dashed lines are not shown here due to the absence of futility boundaries for the Haybittle-Peto design