Dear Freesurfer Mailing List,

I am running a GLM in freesurfer 2 categorical variables (2 levels), and three continuous variables (age, prs, & sles). My fsgd file looks like this:

GroupDescriptorFile 1
Title GLM_sles-group-gender-age
Class genderMale-groupControl
Class genderFemale-groupControl
Class genderMale-groupAtRisk
Class genderFemale-groupAtRisk
Variables age prs sles
Input ID_001 genderFemale-groupAtRisk 20 21 96
Input ID_002 genderFemale-groupControl 21 13 79
...

I want to test for an interaction between prs and sles, while controlling for age, gender, and group. Can you tell me if the following contrast vector will correctly test for this interaction:

0    0    0    0    0    0    0    0    0       0       0       0       0.5    0.5    0.5    0.5
0    0    0    0    0    0    0    0    0.5    0.5    0.5    0.5    0       0       0       0
--

Kind regards,

Bronwyn Overs
Research Assistant

Neuroscience Research Australia
Margarete Ainsworth Building
Barker Street Randwick Sydney NSW 2031 Australia
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