Bioequivalence and Bioavailability Forum

Hi Angus,

❝ Phoenix WinNonlin 6.4 […] I do not see intrasubject and intersubject variances…

Parameters (like the mean & variance) define parametric statistics (hence, the name). Since this test is nonparametric, variance(s) don’t exist.
Don’t get confused by PHX’s output, which gives also the median of test and reference. The PE of T-R is not the difference of these medians. The test calculates all pairwise differences. Their median is called the Hodges-Lehmann estimator; the CI is calculated according to Moses^1,2 (see also this thread). You will also notice that the CI is rarely symmetrical around the PE.

If you want to dive deeper into the matter:

1. Hauschke D, Steinijans VW, Diletti E. A distribution-free procedure for the statistical analysis of bioequivalence studies. Int J Clin Pharm Ther Toxicol. 1990;28(2):72–8. PMID 2307548.
   
2. Hollander M, Wolfe DA. Nonparametric Statistical Methods.New York: Wiley (3rd ed 2013); p. 115–4.