Hi Michael,
Thank you so much for helping me. So that means that I should set up the
design matrices without any covariates for age and gender?
cheers,
Alexander
Michael Harms wrote:
> 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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