Bioequivalence and Bioavailability Forum

Dear Detlew,

❝ Seem again a case that the R geeks have a different opinion as SAS.

Fascinating. 12 subjects, your sequences, EMA all fixed effects, “irrelevant treatments” excluded in Phoenix/WinNonlin:
                        A vs D
                        C vs D              B vs D
Hypothesis       Numer_DF Denom_DF   Numer_DF Denom_DF
int                   1        8          1        9
treatment             1        8          1        9
period                3        8          3        9
sequence              3        8          2        9
sequence*subject      8        8          8        9

❝ More and more I are convinced that statistics is more an art then sciences .

Beyond my intellectual reach. What’s going on here? Three pieces of software treat B/D differently from A/D and C/D.

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Edit: Combinatorial playground. The cells of our pairwise comparisons are:

  A/D        C/D        B/D  
───────    ───────    ───────
• D • A    C D • •    • D B •
D A • •    D • C •    D • • B
• • A D    • C • D    B • • D
A • D •    • • D C    • B D •
───────    ───────    ───────

OK – balanced as expected (each treatment occurs one in each period and the order is twice TR and RT ).

Shuffled:

  A/D        C/D        B/D  
───────    ───────    ───────
· · A D    C D · ·    · B D ·
D A · ·    · · D C    · D B ·
───────    ───────    ───────
A • D ·    · C • D    B • • D
· D • A    D • C ·    D • • B
───────    ───────    ───────

In the upper half of each square treatments immediately follow each other. In the lower half of A/D and C/D they are separated by one excluded treatment – but in B/D they are separated by two…

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   All animals are equal,
but some animals are
more equal than others.   George Orwell (Animal Farm, 1945)