If you want to "eliminate" age and gender, you have to include them in the model. In this case, they are called "nuisance" regressors. But this is just an arbitrary name. The model is constructed of regressors, some of which you care about and some you don't, but the GLM is run in the same way regardless. Where the difference comes is when you go to construct contrast vectors. If you want to treat some regressors as nuisance, then put a 0 in their column in the contrast vector. doug
Antonella Kis wrote:
Hi Doug,
Yes, I looked online but in all the examples I found age was included in the study. The same thing for qdec all the examples I saw online are related to a study (a comparison between two groups) but considering age.
I couldn't find any documentation for a study between two groups while eliminating age and gender.
Please advise and sorry for all this questions. Regards, Antonella
*From:* Douglas N Greve greve@nmr.mgh.harvard.edu *To:* Antonella Kis atorok9@yahoo.com *Cc:* "freesurfer@nmr.mgh.harvard.edu" freesurfer@nmr.mgh.harvard.edu *Sent:* Thursday, September 22, 2011 12:03 PM *Subject:* Re: [Freesurfer] Contrast Vector while eliminating age and gender
Have you looked at the FSGD examples on the wiki? Do a search for FSGD. doug
Antonella Kis wrote:
Dear All,
What should be my contrast vector if I want to do a direct comparison between groups (patients vs. controls) after eliminating gender and age? Should this be [1 -1]?
Should I change my FSGD in order to be able to compare between patients and controls accounting for age (I want to make sure that the age does not confound my results). Please see attached my FSGD file.
Also, my question is how the clusters are created: the clusters formation is due to a similar value within cortical thickness(cortical thickness with similar values from patients and controls are grouped together in a cluster (e.g. cluster no.1) while other cortical thickness values are forming different clusters) or the clusters are formed based on age -age grouping (each subject belong to an age cluster)?
Thank you, AK
-- 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
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