The second design is fine if there is no significant interaction between
1 or 2 and 3. You'll have to create the design matrix yourself or you
can create an fsgd file with 7 classes
On 02/02/2017 11:38 AM, Tim Reess wrote:
>
> Dear Freesurfer experts,
>
> I would like to set up a design matrix for a design that is not
> QDEC-able. I have three categorical factors:
>
> 1.disease status: 2 levels
>
> 2.gender: 2 levels
>
> 3.scan site: 4 levels
>
> The first design I set up was the following (the rows are just for
> illustration and don’t reflect the number of subjects that will enter
> the analysis):
>
> designs4_fs_mailinglist.png
>
> However, I have my doubts as to the “efficiency” of the design (in
> terms of number of regressors / DOF). Therefore, here is my second design:
>
> Would this design be correct for assessing the group differences for
> disease status while regressing out gender and scanner site? My
> understanding is, that in this design I can’t assess the effects of
> interactions regarding scanner site. However, I think it is fair to
> assume that the scanner site doesn’t have a differential effect on
> either gender or disease status. Any feedback is highly appreciated.
> Thanks a lot. Best regards,
>
> Tim
>
>
>
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