Statistical Analysis
organ dysfunction
We estimated that a total sample size of 1400 participants followed up for 30 days would provide 90% power at a 2-sided α = .05 to detect a difference in persistent organ dysfunction–free days following selenium supplementation if the intervention caused a 20% relative increase in the daily rate of liberation from life-sustaining therapy but no change in mortality compared with the control arm. This effect size corresponded to a mean increase of 1.5 persistent organ dysfunction–free days (from 23.2 to 24.7 days). These estimates were based on 10 000 simulations where the control arm followed the distribution of a sample of 170 prior patients who met the current inclusion criteria.For the primary outcome, the van Elteren test stratified by site was used to calculate the 