Bioequivalence and Bioavailability Forum

Dear Detlew & all,

❝ I would nevertheless not state "Small is beautiful".

Correct. I think I was getting the right answer to a wrong question. The CV’s CI helps us to be protected against surprises. In the conventional ABE setting that would mean working with the upper CL, but if scaling comes into play I would say the lower CL is important (lower CV, smaller widening of the AR, higher sample size). My revised example based on CVCL(CV=0.4, df=2*n-3, side="lower"):

pilot n  CLlower
   16    0.326
   20    0.333
   24    0.338
   36    0.348

And sampleN.scABEL(theta0=0.9, CV=CV, design="2x2x3").

  CV   pivotal n  power   total n
0.326      52     0.8082    68
0.333      52     0.8098    72
0.338      52     0.8113    78
0.348      50     0.8028    86

Again smaller pilot sample sizes result in smaller total ones, but your argument about a more precise estimate of the T/R-ratio in larger pilot studies is still valid.