This is treating Dx and Sex as a continuous variable. I've never seen it done before and don't recommend it, but if you want to do it, set up a FSGD file with one group (eg, Main) and two variables. See the FSGD page on the wiki
doug
On 09/05/2013 03:04 PM, Yang, Daniel wrote:
Sex is a nominal variable but can be coded as 0,1.
If it's coded as 0 (male), 1 (female); then the slope means, independent of Diagnosis, how much thicker the brain the female (vs. male) is.
But if I model Sex as a nominal variable, there is always an interaction term between Diagnosis and Sex in qdec, whether DODS or DOSS.
I would prefer not modeling the interaction term, but I don't know how to do so in qdec or mri_glmfit.
Daniel
-- Yung-Jui "Daniel" Yang, PhD Postdoctoral Researcher Yale Child Study Center New Haven, CT (203) 737-5454
On 9/5/13 11:27 AM, "Douglas N Greve" <greve@nmr.mgh.harvard.edu mailto:greve@nmr.mgh.harvard.edu> wrote:
what does a slope of Sex mean? Is Sex a continuous variable? On 09/05/2013 11:03 AM, Yang, Daniel wrote: Hi Doug, So I have two variables: Diagnosis (patient vs. control) and Sex (female vs. male). My model would be: cortical thickness = intercept + (slope1 * Diagnosis) + (slope2 * Sex). Thanks! Daniel -- Yung-Jui "Daniel" Yang, PhD Postdoctoral Researcher Yale Child Study Center New Haven, CT (203) 737-5454 On 9/4/13 10:10 PM, "Douglas Greve" <greve@nmr.mgh.harvard.edu <mailto:greve@nmr.mgh.harvard.edu> <mailto:greve@nmr.mgh.harvard.edu> <mailto:greve@nmr.mgh.harvard.edu%3E>> wrote: I'm not sure you can do that with a linear model. What would your model look like? doug On 9/4/13 9:18 PM, Yang, Daniel wrote: Hi Freesurfer, Is it possible to specify only two main effects but no interaction effect by using mri_glmfit? If yes, could you provide an example? Details are much appreciated! Thanks! Daniel -- Yung-Jui "Daniel" Yang, PhD Postdoctoral Researcher Yale Child Study Center New Haven, CT (203) 737-5454 On 9/3/13 8:45 PM, "Yang, Daniel" <yung-jui.yang@yale.edu <mailto:yung-jui.yang@yale.edu> <mailto:yung-jui.yang@yale.edu> <mailto:yung-jui.yang@yale.edu%3E>> wrote: Dear FS Experts, My model has two categorical variable: Diagnosis and Sex. I am interested in the effect of Diagnosis but I want to control the Sex effect. Toward this goal, I want to model two main effects and want to avoid modeling their interaction term. Is this something feasible in FreeSurfer group analysis? Would using DOSS help with the solution? Thanks! Daniel _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu <mailto:Freesurfer@nmr.mgh.harvard.edu> <mailto: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. _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.eduhttps <mailto:Freesurfer@nmr.mgh.harvard.eduhttps>://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer -- Douglas N. Greve, Ph.D. MGH-NMR Center greve@nmr.mgh.harvard.edu <mailto:greve@nmr.mgh.harvard.edu> Phone Number: 617-724-2358 Fax: 617-726-7422 Bugs: surfer.nmr.mgh.harvard.edu/fswiki/BugReporting FileDrop: https://gate.nmr.mgh.harvard.edu/filedrop2 www.nmr.mgh.harvard.edu/facility/filedrop/index.html Outgoing: ftp://surfer.nmr.mgh.harvard.edu/transfer/outgoing/flat/greve/