Sample size determination for comparison between two means in superiority/equivalence/non-inferiority trails
YUAN Xiao-hong
ZHUANG-Yan
CHEN Ping-yan
Abstract：Objective:To illustrate the effect of two true means difference (μ_A -μ_B) and two types of meth-ods on sample size estimation in equivalence/superiority/non-inferiority trails. Methods; The normal distribution and non-central t distribution separately based methods were applied for sample size estimation,followed by confor-mation using the nQuery Adivisor 7.0. Results : Usually the sample size estimated by the non-central t distribution -based method is 1 - 3 cases larger than that by the normal distribution-based one. The closer to equivalence limits two true means difference is,the larger the sample size is in equivalence trials. The sample size increases with the lager μ_A -μ_B =0 in non-inferiority trials. Conclusion:The assumption of μ_A -μ_B =0 for any sample size estimation in equivalence/non-inferiority trials should not be encouraged because it may lower testing power. The non-central t distribution-based method is recommended to sample size estimation.
Keywords：superiority trialequivalence trialnon-inferiority trialsample size
Publication Date：2009-01-01
Online Publishing Date：2026-08-14(First online date of this platform, not the publication date of the document)
Pages：5( 2205-2209 )