TSD subjects participation in both stages - ANOVA [Two-Stage / GS Designs]

posted by d_labes  – Berlin, Germany, 2015-05-13 11:33 (3560 d 14:57 ago) – Posting: # 14799
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Dear Dan,

additionally and more in depth to what was already said by Helmut and our Capt'n:

IMHO this "interesting" idea has some statistical difficulties.
If you evaluate stage 1 data all is still simple, you have a classical 2x2 crossover with the usual statistical model.

If a second stage is necessary and the sample size estimated for stage 2 is <= n1 you have a replicate design for the subjects having both stage 1 and stage 2 data - four periods, P1 and P2 in stage 1 and the other P3 and P4 in stage 2, i.e. some confounding between period and stage effect. The other subjects having only stage 1 data give a 2x2 design.
Stage itself is no longer a between subject effect but some sort of nested effect. DUNO what sort of, or who is nesting within whom.

The same is true if n2 > n1: you have a replicate design for the n1 subjects having both stage 1 and stage 2 data, and a 2x2 design for those subjects having only stage 2 data.

How the statistical model for such a mixture of different designs with confounding between effects has to be formulated is not obvious to me, especially if one has to include a stage term. See EMA guideline, page 16 "When analysing the combined data from the two stages, a term for stage should be included in the ANOVA model".

I expect all sorts of df=0 or SumOfSquares=0 in the ANOVA decomposition of variance and non-estimable treatment contrasts if one tries to figure out the model by trial and error.

Somebody out there who has a suggestion for a working ANOVA model?
Else the interesting idea has to be thrown into the Thames because we don't know how to evaluate it. Interesting or not.

Regards,

Detlew

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