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An Improvement of the Westlake Symmetric Confidence Interval
Author(s) -
MüllerCohrs J.
Publication year - 1991
Publication title -
biometrical journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.108
H-Index - 63
eISSN - 1521-4036
pISSN - 0323-3847
DOI - 10.1002/bimj.4710330319
Subject(s) - confidence interval , bioequivalence , tolerance interval , mathematics , statistics , confidence region , cdf based nonparametric confidence interval , credible interval , interval (graph theory) , robust confidence intervals , combinatorics , medicine , pharmacokinetics
A common statistical method for assessing bioequivalence of two formulations of a chemical substance is the symmetric confidence interval of W ESTLAKE (1972). As mentioned by W EST ‐L AKE (1981) and S CHUIRMAN (1981) a more powerful method consists of two one‐sided t ‐tests. An (1‐α)‐confidence interval consistent with the two one‐sided t ‐tests procedure is given by [min(α, 0), max (0, b )] where [ a, b ] is the conventional (1–2α)‐confidence interval of the t ‐test. This “central” confidence interval is always a strict subset of the symmetric confidence interval and thus has more power in proving bioequivalence. The central confidence interval has properties comparable with those of the conventional one‐sided confidence intervals.