Hi Alexander,
Given that you are modeling the mean of each subject using a repeated
measures design, that mean already incorporates that subject's age and
gender as part of its estimate. That is, if you added EVs for age
and/or gender, those EVs can be represented as a linear combination of
the columns modeling each subject's overall mean, and thus you would get
a degenerate design matrix. (This wouldn't strictly be true for age IF
the value you used for age differed across the repeated scans of a
subject, but unless your scans were spaced far apart temporally, you
still might get a poorly conditioned design matrix).
cheers,
-MH
On Thu, 2011-05-12 at 01:12 +0100, Alexander Olsen wrote:
> Dear FLS experts,
>
> I'm struggling a bit with setting up my analysis. What I would like to do is a repeated measures design with four timepoints, as in this example:
>
> http://www.fmrib.ox.ac.uk/fsl/feat5/detail.html#ANOVA1factor4levelsRepeatedMeasures
>
> However, I would also like to add age and gender as covariates in order to "remove" these effects. I hope anyone can help me, or direct me to an example which describes this.
>
> Thank you so much in advance.
>
> Alexander
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