## WHO lamenting about terminology? [Regulatives / Guidelines]

Dear Detlew,

» Of course the two calculations are different, no doubt about it.

Like $$\small{2+2+2+2=2\times4=2^3=8}$$. Different calculations, same result.

» I have understood “operationally identical” always as the fact that TOST and CI inclusion give the same answer with regard to the BE decision.

Acc. to Berger and Hsu not sure about the “always”. But that’s another story and of historical interest only.

» IMHO this is the meaning of the paragraph on page 661 in Donalds famous paper containing “operationally identical”:
» "The two one-sided tests procedure turns out to be operationally identical to the procedure of declaring equivalence only if the ordinary 1 - 2α (not 1-α) confidence interval for µT-µR is completely contained in the equivalence interval [θ1, θ2]".
» Emphasis by me.

Correct. Also in Chow and Liu (p.98):

The two one-sided t tests procedure is operationally equivalent to the classic (shortest) confidence interval approach; that is, if the classic (1–2α)100% confidence interval for μTμR is within (θL, θU), then both H01 and H02 are also rejected at the α level by the two one-sided t tests procedure.

Coming back to the WHO’s rant:

The calculation of the 90% confidence interval (CI) of the mean test/comparator ratio for the primary PK parameters should not be confused with the two one-sided t-tests employed to reject the null hypothesis of non-equivalence. The end result is the same, but these are not the same calculations.

IMHO, they are just fed up reading “TOST” whilst the CI inclusion approach acc. to the GL was actually performed.
• Strict TOST (p-values only): Deficiency letter “Where is the CI?”
• Claiming TOST, reporting the CI: Sloppy terminology, copy&paste from the dark ages?

Dif-tor heh smusma 🖖
Helmut Schütz

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