Bioequivalence and Bioavailability Forum

Dear Bears,

❝ Here are some results generated from bear v2.3.0.

» <<Sample Size Estimation>>

❝

❝  Upper acceptance limit = 125 %
❝  Lower acceptance limit = 80 %
❝      Expected ratio T/R = 95.00 %
❝            Target power = 80.00 %

❝ Inter- or Intra-subj CV = 20.0 %

❝

❝  study    2x2x1         2x2x2        2x2x3        2x2x4

❝ design   parallel     crossover   replicated   replicated

❝ ------- ----------- ------------ ------------ ------------

❝    N       36            20           16           10

From the methodological and educational point of view I would suggest not to mention parallel group design side by side with the cross-over designs.

These a so different pairs of shoes because of the different variabilities involved. The "naive" user may be mislead in choosing his right design.

To illustrate what I mean let's argue "naive":
The cost for one subject in a BE study is mainly determined by observing the concentration time course. For the parallel group design we have 36 concentration time course to observe. For the 2x2x2 crossover we have 20 in period one and 20 in period 2. So concerning our budget (too small for the study, as usual ) we choose of course the parallel group design.

Of course this argument is not for the informed users who knows what he does. But ...
It needs only a short look into the sample size category of this forum ...