No alternative [Power / Sample Size]

posted by d_labes  – Berlin, Germany, 2017-02-09 20:37  – Posting: # 17047
Views: 19,141

Dear Helmut!

» As zizou noted above it is less informative than the conventional (shortest) CI

Ever used the 'more informative' feature really?
Beside the need to answer questions "Why does the CI not covering 1" aka "please discuss the significant treatment effect"? And answering along the line "significant treatment effect is not the question to be answered in an equivalence trial and therefore not relevant"?

» – we only know that the GMR is <1 - and we can’t calculate the CV from the CI any more.

Really? Why not?
I could :cool: and PowerTOST also, presumed I have the point estimate at hand.

Additionally being able to re-calculate the CV from the CI is a "nice to have", but not a pre-requisite for a valid decision procedure of the (bio)equivalence.

To be clear: I don't advocate to use the alternative CI. It has it's pros and cons like the conventional 1-2*alpha CI also has it's pros and cons. See the Berger/Hsu paper and similar research. But it illustrates in my opinion that the request "GMR=1 has to be in the (whatever) CI" is superflous. It may be included in the BE devision via that alternative CI in a straight forward matter or if included in the conventional CI lead to a BE decision procedure with horrible power and ultra-conservative type I error as zizou has excellently schown and as we dicussed above. Features which renders this BE decision procedure as nearly unfeasible.

Moreover: The 1-2*alpha CI has made it, in the community of BE researchers as well as into the regulatory boddies. Thus we have no choice ... Whatever we like or like not. We are all sheeps ...

So much ado for nothing.
Drink milk or better drink a good Czech beer, preferrably from zizou's home :party:.

Regards,

Detlew

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