Hi Freesurfers,
I am trying to set up both a 2 Group 1 Covariate and a 4 Group 1
Covariate analysis but just want to make sure I'm using the correct
contrast option.
For the first analyis, the two groups are Drug Pre and Drug Post,
with folate-serum level as a covaraite. We want to keep the covariate
under consideration in our analyses, but we really want to look at
the difference between the Drug Pre and Drug Post activation (so
folate-serum level is more of a nuisance variable). It seems that the
first option under the 2G1V Page "Null Hypothesis: is there a
difference between the group intercepts? Is there a difference
between groups regressing out the effect of age? 1 -1 0 0"
reflects this idea best.
For the second analysis, the 4 Groups are Drug Pre, Drug Post,
Placebo Pre, and Placebo Post, with the same folate-serum level
covariate. We are intersted in the double subtraction of (Drug Post
- Drug Pre) MINUS (Placebo Post - Placebo Pre), but again wish to
covary by folate level. For this it seems like contast 7 on the 4G1V
page "is there an interaction between gender and handedness
regressing out the effects of age? 0.5 -0.5 -0.5 0.5 0 0 0
0" is best.
Is this the best way to go about analyzing these two questions?
Thanks,
Adam Nitenson, B.S.
Brain Genomics Lab
Massachusetts General Hospital
niten...@nmr.mgh.harvard.edu
Phone: 617-643-3215
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