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Total study sample size required for 90% power (using a two-sided chi-squared test with Type I error=0.05) using intention-to-treat analysis, according to relative corticosteroid benefit when used as “rescue” therapy (horizontal axis) and to proportion of placebo arm subjects crossing over to “rescue” therapy (10% to 50%, as labeled on each curve). The risk of mortality among crossovers from placebo, if “rescue” therapy not given, is assumed to be 50%. Tx denotes treatment.
