Mehul Sampat wrote: > Hi FS folks, > > I have a basic GLM question. I went through the tutorials online but I > was not sure and wanted to check with someone. > > I am trying to compare the cortical thickness between a group of > patients (n = 166) and controls (n = 76). > > For patients mean age is 49.8 +/- 9.1 and there are 55 Male; 111 Female > For controls mean age is 40.5 +/- 11.4 and there are 26 Male; 50 Female > > If include gender as a fixed factor does the output of the GLM answer > the following: > 1. "Is the cortical thickness different between the patients and > controls accounting for gender" All the factors in mri_glmfit/QDEC are random factors. But, yes, it would answer that question. > > 2. As I understand the GLM setup one can control for gender and other > discrete factors but not for continuous co-variates such as age ? > That is one can find the association between thickness and age and see > if it is different for the two groups. > However if the age distributions for the two groups are different one > cannot control for it with GLM. is this interpretation correct ? Not quite. You can always put age in as a continuous covariate. If there are effects of age or an interaction between age and group, then there are some subtle statistical issues.
doug > > If so, how would one control for age in such an analysis ? > > Any help is much appreciated. > > Thanks > Mehul > > > > > 2. For the correction of multiple comparisons, when should one use FDR > as compared to monte-carlo simulations ? > > Thanks > Mehul > > > ------------------------------------------------------------------------ > > _______________________________________________ > Freesurfer mailing list > [email protected] > https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer -- Douglas N. Greve, Ph.D. MGH-NMR Center [email protected] Phone Number: 617-724-2358 Fax: 617-726-7422 In order to help us help you, please follow the steps in: surfer.nmr.mgh.harvard.edu/fswiki/BugReporting _______________________________________________ Freesurfer mailing list [email protected] https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
