... efficacy in trials in critical caremedicine, a finding the authors attributed to the use of mortality as an endpoint [1]. We extend this work byidentifying a key feature of such trials, namely that ... Shu V, Zwingelstein C, Tobias J, Poole L, Stolzenbach JC, Creasey AA, OPTIMIST Trial Study Group: Efficacy and safety of tifacogin (recombinant tissue factor pathway inhibitor) in severe sepsis: ... be chosen by investigators in the design of a trial of mortality in order to determine therequired sample size, including the significance levelrequired for rejection of the null hypothesis;...