Hi FS community,
I had a few questions regarding my understanding of the group analysis in FS:
1) If I use an fsgd file with Two Groups (One Factor/Two Levels), No Covariates, and my contrast matrix is [1 -1], do the resulting clusters (if any) show the regional significant differences between the two groups by comparing just the means of the values that I am comparing? For instance, if I'm comparing cortical thickness between a diseased and a control group, is this going to give me the clusters where the Diseased subjects' (no age included in the fsgd file, just the two groups) mean/regional cortical thickness differs significantly from the controls'? In other words, is a 50 yo subject's mean/regional cortical thickness going to be treated the same as a 80 yo subject's?
2) Now suppose that I would like to control for age. Then I'm assuming that I need to create an fsgd file with two Groups (One Factor/Two Levels) and One Covariate (age). Similarly, if I would want to visualize the differences in the regional values of cortical thickness between the two groups but after they have been controlled/adjusted for age, what contrast matrix should I use? Normally I would use [0 0 1 -1] but this will give me the significant differences in the age slopes not the mean values, unless I am missing something here.
Thanks in advance for your help and sorry for the lengthy message.
Best, Panos