Equivalence and non-inferiority

This chapter looks at methods for the evaluation of equivalence and non‐inferiority. The first step in establishing equivalence is to define what one means by equivalence. The next step is to undertake the trial and calculate the 95 per cent confidence interval for the difference in the means. For non‐inferiority, the first step involves defining a non‐inferiority margin. Step two is then to run the trial and compute the 95 per cent confidence interval for the difference μ1 − μ2, in the mean reductions in diastolic blood pressure. The inclusion of a placebo arm would allow direct evaluation of assay sensitivity. One crucial quantity in the sample size calculation for a non‐inferiority trial is Δ, which plays a role similar to the clinically relevant difference (crd) in a superiority sample size calculation.