Non-inferiority tests for comparing two binomial proportions are frequently used in clinical trials to prove that a new drug with few side effects or low cost is not significantly inferior in efficacy to the standard drug [1-3]. The Blackwelder [4] procedure is commonly used to calculate the sample size for non-inferiority clinical trials. This paper presents a derivation of the Blackwelder sample size formula.

no-inferiority tests, sample size, comparing binomial proportions.