Your interpretation of the beta.mgh file is correct. That contrast will compute the difference of the groups. Not sure what you mean by the "slope of the difference".
doug
jorge luis wrote:
Hello all
We are comparing the cortical thickness of two groups with the following fsgd file:
GroupDescriptorFile 1 Title Thickness-subj Class contr Class modif
Input subj1 contr Input subj2 contr Input subj3 contr Input subj4 contr ... Input subj36 modif Input subj37 modif Input subj38 modif Input subj39 modif ...
(the same number of subjects) We are using the contrast vector: 1 -1 and DOSS codification for the design matrix.
The generated beta.mgh file contains two frames, I think one is for the coefficients of the first regressor and the other is for the coefficients of the second one.
Now we want to infer the groups difference in cortical thickness at each 'activated' vertice (the change in mm).
Can we do that by simply taking de difference between thouse first and second regression coefficients?
I think this value can be seen as the slope of the difference between the first and the second group. Is it true?
Any tip is welcome In advance thank you
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