Thanks for your help. I've noticed, however, that 2 of the centres contribute a smaller number of subjects and don't in fact have any female controls. Should I remove these as classes (ie. take out control_Female_centre1 and control_Female_centre2) and then change the subsequent contrast file to look like: 1 1 1 1 1 1 1 1 1 1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 0 Or would this be a problem since now the number of classes that are controls or patients are uneven (10 vs. 12)?
Thanks again, Colleen --- Colleen Rollins, PhD Candidate Department of Psychiatry University of Cambridge Herchel Smith Building, Robinson Way, Cambridge CB2 0SZ On 2018-04-09 14:50, C.P.E. Rollins wrote: > Hi Douglas, > > Thanks for your response. I just wanted to confirm how the FSGD and > contrast files might look for the multicentre study. If I'm to create > a separate class for each combination of diagnosis, sex, and center, > would there then be 24 classes? (as there are 2 diagnoses (patient vs. > control), 2 sex, and 6 centres). > For instance: > GroupDescriptorFile 1 > Group control_Male_centre1 > Group control_Female_centre1 > Group control_Male_centre2 > Group control_Female_centre2 > Group control_Male_centre3 > Group control_Female_centre3 > Group control_Male_centre4 > Group control_Female_centre4 > Group control_Male_centre5 > Group control_Female_centre5 > Group control_Male_centre6 > Group control_Female_centre6 > Group patient_Male_centre1 > Group patient_Female_centre1 > Group patient_Male_centre2 > Group patient_Female_centre2 > ... > > Then, my contrast between patients and controls would look like > 1 1 1 1 1 1 1 1 1 1 1 1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 0 > for a doss model, if I'm additionally controlling for age, or 24 zeros > (instead of 1) for a dods model? > Moreover, should I expect any issues with using such a high number of > classes? > > Thanks again, > Colleen _______________________________________________ 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.