Bioequivalence and Bioavailability Forum

Dear John,

What does the poet want to tell us? (An old question from school days.)

I didn't criticized the chosen Latin square. IMHO it is not necessary to choose a Williams square which is said to be balanced with respect to 'first order carry over' since our usual evaluation does not consider such an effect. Beside the fact that 'first order carry over' is highly criticized (see Stephen Senn's book "Cross-over Trials in Clinical Research").
The use of Williams design is nevertheless often used nowadays because of historical reasons.

What I tried to say was that your code results in a 'random' list which was a simple repetition of the four sequences, i.e subjects 1-4 were assigned to the four sequences, subjects 8-12 to the same four sequences and so on.
Try the code
proc plan seed=12152;
  factors Subject=24 random Period=4 ordered;
  treatments Treatment=4 cyclic;
  output out=LatinSquare
  Treatment cvals=('A' 'B' 'C' 'D') random;
run;
to see the difference.