Bioequivalence and Bioavailability Forum

Hi Helmut,

❝ what’s the distribution of concentrations (or derived metrics like AUC)? AUC seems to be log-normal (see here). I dunno whether anybody explored concentrations. If we don’t believe in exotic matter (e.g., negative mass) truncation at zero (or LLOQ?) makes sense. Or is the distribution log-normal? Probably (will pool some data time allowing). Note that in PopPK an error model with censored data is often used.

Good input. I have no idea myself. I live in a cage. Whether or not something is relevant to real life is of no particular interest to me

At this point in principle any distribution would suffice for starters as long as:

1. I can control the geometric mean.
   
2. I can control the CV.
   
3. The dist. is not log normal.
   
4. I can derive random numbers via pts 1+2.

Having said all that I need to air another thought:
We usually say that the error of the linear model is IID and normal with mean zero but actually Chow and Liu's formulation in that regard is not crystal clear. You showed some beautiful plots -can't find the thread right now- which demonstrated that the errors are correlated within subject. I am inclined to think that we do not strictly need IID for the normal linear model. We can relax it a bit:
we only need IID for the difference of test-ref in xovers, and that's why the Potvin/Montague considerations actually work.

Parallel is another matter of course.

Hell, I wish I had studied statistics at the university.





I think the