Bioequivalence and Bioavailability Forum

Dear yicaoting, dear all,

❝ ----------From PNX WNL User Guide P341-342----------------------------------Power

❝ ...

❝ In the bioequivalence calculations, the hypotheses being tested are:

❝

❝ H₀: RefLSM = TestLSM

❝ H₁: RefLSM ≠ TestLSM

❝ ...

This explains all! These hypotheses are for a superiority test or test for difference! Thus the first sentence should correctly read "In the bioequivalence calculations, the hypotheses not being tested ..."

In BE testing we are interested in testing the reversed hypotheses, i.e. the Null is inequivalence, the Alternative is equivalence RefLSM = TestLSM (within some reasonable chosen margins).

This explains why the power given in WLN is higher then calculated by PowerTOST. It's well known that the superiority test has higher power than the equivalence or non-inferiority test.

The formulas given by yicaoting point in the same direction (power for a test of difference), but complicated by the fact that not the usual non-central t-distribution is used in the power calculation but an approximation via 'shifted' central t distribution.
I can't reproduce the numbers because I don't have RefLSM and the DiffSE. Yicaoting, be so kind to post them here.

To answer the question

❝ Dear all, True or False of WNL's method?

I would state: Approximate correct for the problem stated but answers a question no one has asked .