Group effects EMA [Two-Stage / GS Designs]

posted by ElMaestro  – Belgium?, 2016-10-07 12:45 (1400 d 04:33 ago) – Posting: # 16705
Views: 29,287

Hi VStus,

» I have performed exercise on this dataset in R and have to support Mittyri: addition of more effects beyond group increases MSE and, therefore, CI: (...)

Hehe, this is a truly remarkable phenomenon.
Inclusion of more factors or more crosses/nestings introduces new columns in the muddle matrix, so the residual variability measured as SS decreases. Nevertheless, the residual variance, MSE or SS divided by DF, may go up as the new columns in the muddle matrix steals a bit from the DF pool. You should see that if you do an anova on your model object.
Quite possibly, you are right in theory the width of the CI could in such cases increase? I did not recalculate it in this case, perhaps that is really possible?!?
I doubt it would happen with biological data, but I see now I should not have stated it like I did in the post above. I apologise for any confusion my post led to.

» Due to my limited R knowledge, I cannot figure out how to add other effects recommended by FDA e.g. subject(sequence x group), but I'm afraid that at least in R, the more related effects - the wider confidence intervals...

You are ok as long as you code subjects uniquely, then it does not matter if you call them Subject or Subject in Sequence in Group etc. Search this forum for the famous Silly-o-meter and it will be crystal clear, of course. :-D:-D:-D:-D:-D


A good weekend to all of you.

I could be wrong, but...

Best regards,

"Pass or fail" (D. Potvin et al., 2008)

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