It depends on the order that you specified them. You will have four groups SczUrban SczRural HVUrban HVRural

The interaction will be of the form (SczUrban-SczRural)-(HVUrban-HVRural)

Look in the y.fsgd to see what the order of the classes is. You can then look in the contrast folder at C.dat to get the + and - 1s used in the contrast.

On 12/9/2020 12:58 PM, vittal korann wrote:

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Dear FreeSurfer experts,

I was running group interaction (for diagnosis and birthplace) in QDEC with gyrification as a dependent variable and age, gender as nuisance factors. In diagnosis, we have 2 groups: i) schizophrenic patients ii) healthy volunteers. Similarly, birthplace has 2 groups: i) urban ii) rural birth

For the above-said design, I got reddish yellow color results in the display tab of Qdec. So, my query is that do results indicate that patients who were born in urban have a higher gyrification index than healthy volunteers who born in urban or something else? Do I sound correct in decoding the interaction results? If not please let me know the exact meaning of the results.

Looking forward to hearing from you.

Thanks, Vittal

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