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Table 2 Approximate sample sizes required for non-inferiority comparison of proportions

From: Through the looking glass: understanding non-inferiority

True proportion in active control Non-inferiority bound using 10% margin Approximate sample size per group assuming 1:1 randomization to new treatment and control required under:
   Equal effects 5% benefit 10% benefit
0.1 0.09 19,200 8,725 5,050
0.2 0.18 8,500 3,900 2,250
0.3 0.27 4,970 2,260 1,300
0.4 0.36 3,200 1,450 825
0.5 0.45 2,100 1,000 550
0.6 0.54 1,440 640 360
0.7 0.63 930 405 225
  1. Sample sizes calculated using Pass 2008 methods for non-inferiority tests of two independent proportions, using the Z statistic with continuity correction and pooled variance, with a target power of 90% and α level of 0.025.