Dear Serge,
> I am trying to do a second level analysis with repeated measures per
> subject. The simplified version is:
> a group of 10 subjects, consisting of two subgroups of 5 subjects each, and
> 2 copes per subject (in reality I have 3 groups, 87 subjects and 7 copes).
>
> Copes were generated using a model with orthogonal regressors at first
> level.
> I want to apply an analysis with 2 repetitions per subjects (the two copes)
> and test whether cope1 distinguishes the two subgroups of 5 subjects better
> than cope 2.
> My design then is as follows:
> group EV1 EV2 EV3
> EV4 ... EV12
> subject 1, cope 1 1 1 0 1
> 0 0
> subject 1, cope 2 1 0 1 1
> 0 0
> subject 2, cope 1 1 1 0 0
> 1 0
> subject 2, cope 2 1 0 1 0
> 1 0
>
> ......
>
> subject 9, cope 1 1 -1 0 0
> 0 0
> subject 9, cope 2 1 0 -1 0
> 0 0
> subject 10, cope 1 1 -1 0 0
> 0 1
> subjects 10, cope 2 1 0 -1 0
> 0 1
> Contrasts:
> 1 0 0 0 0 0 0 0 0 0 0 0 : first 5 subjects > last 5 subjects for cope 1
>
> 0 1 0 0 0 0 0 0 0 0 0 0 : the same for cope 2
>
> 1 -1 0 0 0 0 0 0 0 0 0 0: is the difference between the two subgroups
> greater for cope 1 than for cope 2?
>
> etcetera
I cannot see why you have included EVs for subject means (EVs 3-12).
You should replace them with EVs for the cope means:
group EV1 EV2 EV3 EV4
subject 1, cope 1 1 1 0 1 0
subject 1, cope 2 1 0 1 0 1
subject 2, cope 1 1 1 0 1 0
subject 2, cope 2 1 0 1 0 1
......
subject 9, cope 1 1 -1 0 1 0
subject 9, cope 2 1 0 -1 0 1
subject 10, cope 1 1 -1 0 1 0
subjects 10, cope 2 1 0 -1 0 1
then a [1 -1 0 0] contrast should give you what I think you are after.
> So far I am happy with my design. But I need to include one covariate for
> age and one for gender as well. The demeaned age EV (EV13) would be
> something like:
> 12
> 12
> -7
> -7
> ...
> -11
> -11
> 6
> 6
Yes, you can simply put this in as an extra EV.
> To avoid rank deficiency, I can remove EV12 (the EV of subject 10), but I am
> not sure whether this is allowed.
with EVs3-12 removed this shouldn't be a problem.
Best Regards,
Mark Woolrich.
