I think this is the contrast you need

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

On 10/19/2014 06:33 PM, Bronwyn Overs wrote:

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

Neuroscience Research Australia
Margarete Ainsworth Building
Barker Street Randwick Sydney NSW 2031 Australia
*M* 0411 308 769 *T* +61 2 9399 1883 *F* +61 2 9399 1265

neura.edu.au <http://neura.edu.au>

Follow @neuraustralia on twitter 
<https://twitter.com/neuraustralia>Follow NeuRA on facebook 
<https://www.facebook.com/NeuroscienceResearchAustralia>Subscribe to 
the NeuRA Magazine <http://www.neura.edu.au/help-research/subscribe>

_______________________________________________
Freesurfer mailing list
Freesurfer@nmr.mgh.harvard.edu
https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer