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Non-Inferiority (Means) Sample Size Calculator

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Calculate the sample size needed to demonstrate that a new treatment is not worse than the standard by a pre-specified margin.

Study Parameters
Results

Required Sample Size

126

Group 1: 63 | Group 2: 63

Achieved Power

80.1%

Effect Size

0.500

Method: Non-Inferiority Test for Means (One-sided)
NI margin5
Expected difference0
Standardized offset0.500
  • •Independent samples
  • •Normally distributed outcomes
  • •Equal variances in both groups
  • •One-sided test (non-inferiority is inherently one-sided)
  • •Non-inferiority margin Delta_NI = 5
Formula
n = (z_alpha + z_beta)^2 * 2 * sigma^2 / (delta + Delta_NI)^2
References
  1. Chow SC, Shao J, Wang H (2008). Sample Size Calculations in Clinical Research, 2nd ed. Chapman & Hall/CRC.
  2. FDA Guidance: Non-Inferiority Clinical Trials to Establish Effectiveness (2016).