Correction to: Optimality criteria for futility stopping boundaries for group sequential designs with a continuous endpoint.

An amendment to this paper has been published and can be accessed via the original article.

Correction to: BMC Med Res Methodol 20, 274 (2020)

https://doi.org/10.1186/s12874-020-01141-5

Following publication of the article [1], it was noted that due to a typesetting error the old version of Fig. 1 is displayed with the correct version of Fig. 1, and it should be deleted.

Fig. 1

The “optimal” futility boundary α0,opt as a function of the admissible parameters Pow and π for N = 140 (blue dots) and n = 188 (red squares). The black symbols highlight the “optimal” futility boundaries for Powloss = 0.05 and πwrong = 0.05

The correct Fig. 1 and caption have been included in this correction, and the original article has been corrected.