Hi, I am trying to run a cortical thickness analysis comparing four groups – my goal is to conduct an omnibus F-test testing for any group differences. I have 0 covariates/nuisance regressors.
This would be equivalent to the “Contrast 4 group.effect.mtx” in this page, for 3 groups: https://surfer.nmr.mgh.harvard.edu/fswiki/Fsgdf3G0V But, instead of 3 groups I have 4 groups. I thought the contrast matrix for 4 groups F-test would be: 1 -1 0 0 0 1 -1 0 0 0 1 -1 But for 3 groups it is: 1 -1 0 1 0 -1 Would you please clarify the correct contrast matrix for this test in Freesurfer mri_glmfit? Thank you! Andrea -- Andrea Gold, Ph.D. Section on Development and Affective Neuroscience National Institute of Mental Health 9000 Rockville Pike MSC 2670 Bldg. 15K Bethesda, MD 20892 Phone: 301-402-6955 Fax: 301-402-2010 Email: andrea.g...@nih.gov
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