Bioequivalence and Bioavailability Forum

Hi BE-proff,

❝ I will try to reformulate the question :)

Sorry if I did not catch your point. Happens very often
Being equipped with a walnut-sized brain I am what is typically called an anatomical, cerebral and intellectual anomaly. It does pose some social challenges too. I am obviously born 150 years too late. In 1866 I could probably have been a star in a freak show somewhere.

❝ If my prior results show 0.81-1.02 I will think that the current formulation is risky for the 2nd study but I don't have any figures to assess the risk.

❝

❝ Sqrt(0.81x1.02) returns 0.909...does it give me anything useful for brain?

Then 0.909 is your point estimate. It would be good if the true GMR is 1.02 and it would be bad if the GMR is 0.81. With the usual assumptions blahblah 1.02 is as likely as 0.81. 0.909 is probably your best guess for the time being, right? People would call that the GMR of maximum likelihood.
There was a crazy scientist a few years back who published something about two studies in a row. Something with power, type I errors, and how one can make use of the first study info to plan the second trial. There is a link to the paper (free) here. Try and see if the answer to your question might be in the paper.

However, I'd like to stress that the most important conclusion that was made -and this is hardly news if your think about it- is that when there is uncertainty about the GMR then it is not often wise or reasonable to base any planning on its estimate. And that's how a small pilot trial easily is about as good as no study.