Thank you for the information. I just want to be sure if I have understood it properly. If I had two groups and two sites, my design matrix would be like:
GroupDescriptorFile 1 Class PatientsGroup1 Class PatientsGroup2 Class ControlsGroup1 Class ControlsGroup2 If I want to test for the effect of group, contrast matrix would be: 0.5 -0.5 0.5 -0.5 If I want to test for the effect of site, contrast matrix would be: 0.5 0.5 -0.5 -0.5 Finally, in case of interaction test, how contrast matrix would be? Douglas N Greve <gr...@nmr.mgh.harvard.edu> escribió: > You should make sure to have a balanced design (ie, approx the same pats > and cons at each site). Then include site as a regressor, ie, if you had > two groups and two sites, you would have four regressors. You could > then test for the effect of group, the effect of site, and the > interaction. If there is an interaction, then it is hard to interpret > the differences between groups. > _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer The information in this e-mail is intended only for the person to whom it is addressed. If you believe this e-mail was sent to you in error and the e-mail contains patient information, please contact the Partners Compliance HelpLine at http://www.partners.org/complianceline . If the e-mail was sent to you in error but does not contain patient information, please contact the sender and properly dispose of the e-mail.
