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Non-Inferiority (Proportions) Sample Size Calculator

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Calculate the sample size needed for a non-inferiority trial comparing two proportions using the Wald method.

Study Parameters
Results

Required Sample Size

634

Group 1: 317 | Group 2: 317

Achieved Power

80.1%

Effect Size

0.100

Method: Non-Inferiority Test for Proportions (Wald Method)
NI margin0.100
Expected difference (p_T - p_C)0.000
Distance from boundary0.100
  • •Independent samples
  • •Binary outcomes
  • •One-sided test (non-inferiority)
  • •Non-inferiority margin Delta_NI = 0.1
  • •Wald method approximation for variance under H0
Formula
n = [z_alpha * sqrt(V_H0) + z_beta * sqrt(V_H1)]^2 / (delta + Delta_NI)^2
References
  1. Farrington CP, Manning G (1990). Test statistics and sample size formulae for comparative binomial trials. Statistics in Medicine, 9, 1447-1454.
  2. Blackwelder WC (1982). "Proving the null hypothesis" in clinical trials. Controlled Clinical Trials, 3, 345-353.