Bioequivalence and Bioavailability Forum

Dear John,

❝ Can someone run powerTOST in R to confirm the ISCV from the following:

Of course .

Without repeating the numbers, my results are of course exactly the same as yours. Wouldn't expect something different since we are using the same software.

❝ The result for 2 and 3 is a bit strange.

Why? What is wrong with a 3.2% difference. IMHO not really big. Humans usually recognize 10% as a difference, f.i. 10 cent of a dollar, to desist from nickel nursers or from the Scotch (Beg your pardon Scotch ).

One caveat! From the documentation of CVfromCI():"It is assumed that the sequence groups in a crossover study or the treatment arms in a parallel-group study are balanced. The estimated CV is conservative (i.e. greater than actually observed) in case of unbalanced studies." Emphasis by me.

You may check this (your studies are unbalanced) if you recalculate the CI's from the point estimators, n and the obtained CV. Example 2 of your post:
n  <- 55
df <- n-3 # robust
bk <- 1.5 # design constant for 2x3x3
CV <- 0.2905871
point <- 0.8557
# CI in the log-transformed domain
CI <- log(point) + c(-1,1)*qt(0.95,df)*sqrt(bk*CV2mse(CV)/n)
CI <- exp(CI) # back transformation
gives nearly the same interval than the original:
0.7909039 0.9258046 # back calculated
0.7909    0.9258    # original
Seems the un-balancedness is not a problem here.