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Table 2 Sample size required by event rates

From: Baby-OSCAR: Outcome after Selective early treatment for Closure of patent ductus ARteriosus in preterm babies—a statistical analysis plan for short-term outcomes

Control group event rate Active Rx group event rate Absolute risk reduction Relative risk reduction Approximate total sample size required
60% 47% 13% 22% 620
60% 48% 12% 20% 730
60% 49% 11% 18% 870