A review and re-interpretation of a group-sequential approach to sample size re-estimation in two-stage trials.
Bottom Line: In this paper, we review the adaptive design methodology of Li et al. (Biostatistics 3:277-287) for two-stage trials with mid-trial sample size adjustment.We argue that it is closer in principle to a group sequential design, in spite of its obvious adaptive element.Several extensions are proposed that aim to make it even more attractive and transparent alternative to a standard (fixed sample size) trial for funding bodies to consider.
Affiliation: MRC Biostatistics Unit, Cambridge, UK.Show MeSH
Mentions: Figure 5 compares the operating characteristics four designs featured. Designs 1 and 2 have a far smaller expected sample size than 3 and 4 but because of this, do not control the overall power at at the original desired level of 80%. As well as being identical to the fixed design at δ = , the unconditional power curves of designs 3 and 4 are very close to that of the fixed design across all values of δ.