Bioequivalence and Bioavailability Forum

Dear ElMaestro!

To add my two cents:
The original sample size tables of Diletti et al. [1] contain the target powers 70, 80 and 90%. Thus these Authors must had the feeling that 70% is a reasonable lower bound. That's also my feeling. But at the end it's a question what risk of erroneous not concluding BE the sponsor is willing to accept.

The usual 80% power to attain is only a convention like 5% alpha. But had made it into regulations.
The source of this number was already stated by Dan.

But I would not give a cut-off value as futile because I think that a target power of f.i. 0.778 is equal sufficient like 0.8.
As we all know the power is highly dependent on our presumptions concerning variability and true GMR. If we miss them to some extent in the real outcome of our study we are always in danger of having not correctly powered the study.
This is the case for the sensitivity analysis of sample size planning Helmut is not tired to preach every time.


[1] Diletti E, Hauschke D, Steinijans VW
Sample Size Determination for Bioequivalence Assessment by Means of Confidence Intervals
Int. J. Clin. Pharm. Ther. Tox., Vol. 30 Supl. 1, S51-58, 1992