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Table 3 Evaluable sample size estimates

From: A description of the methods of the aspirin supplementation for pregnancy indicated risk reduction in nulliparas (ASPIRIN) study

PTB rate in Placebo Arm PTB rate in ASA % Red. Sample size per group PTB rate in ASA % Red. Sample size per group PTB rate in ASA % Red. Sample size per group
Power = 80% (α = 0.05; β = 0.2)
 8% 4.8% 40% 918 6.0% 25% 2554 6.40% 20% 4096
 10% 6.0% 40% 721 7.5% 25% 2005 8.00% 20% 3213
 12% 7.2% 40% 591 9.0% 25% 1638 9.60% 20% 2625
 14% 8.4% 40% 497 10.0% 25% 1377 11.20% 20% 2204
Power = 90% (α = 0.05; β = 0.1)
 8% 4.8% 40% 1228 6.0% 25% 3419 6.40% 20% 5483
 10% 6.0% 40% 965 7.5% 25% 2683 8.00% 20% 4301
 12% 7.2% 40% 790 9.0% 25% 2193 9.60% 20% 3513
 14% 8.4% 40% 665 10.5% 25% 1842 11.20% 20% 2950