i think you would still run into the same probem
On 07/11/2017 12:15 PM, Yann Ying Chye wrote: > Thanks for your reply, > > I have a follow up on my first question - if however I was not looking > for a main effect of gender, but for the main effect of something else > (e.g. diagnosis), will it then be ok to include the unbalanced group > (i.e. A-male), to control for gender? > > Thanks! > > Regards > Yann > > On 7 July 2017 at 18:34, <freesurfer-requ...@nmr.mgh.harvard.edu > <mailto:freesurfer-requ...@nmr.mgh.harvard.edu>> wrote: > > Send Freesurfer mailing list submissions to > freesurfer@nmr.mgh.harvard.edu <mailto:freesurfer@nmr.mgh.harvard.edu> > > To subscribe or unsubscribe via the World Wide Web, visit > https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer > <https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer> > or, via email, send a message with subject or body 'help' to > freesurfer-requ...@nmr.mgh.harvard.edu > <mailto:freesurfer-requ...@nmr.mgh.harvard.edu> > > You can reach the person managing the list at > freesurfer-ow...@nmr.mgh.harvard.edu > <mailto:freesurfer-ow...@nmr.mgh.harvard.edu> > > > > On 7/7/17 1:58 PM, Yann Ying Chye wrote: > > Dear FreeSurfer mailing list, > > > > I've got two questions regarding the freesurfer GLM analysis. > > > > 1. I am trying to run mri_glmfit on the cortical thickness of a > > dataset that has a few interacting factors of unequal levels. > > For example, my dataset may have groups A, B, C, and D. Within the > > groups, subjects are further divided by gender - male and female. > > However, group A only has males, such that the classes in my > FSGD file > > = A-male, B-male, B-female, C-male, C-female, D-male, and D-female. > > Will this design be a problem? Will it be statistically sound? > > Additionally if I was looking for an effect of gender, how would I > > weigh my contrast? I was thinking 0.25 0.25 -0.33 0.25 -0.33 0.25 > > -0.33. Would that be valid? > I think I would lean against including A-male. Otherwise, what is the > null hypothesis? Without A-male, it would be that males and females > differ when regeressing out the effect of group, but you can't say > that > if you include A-male. Eg, if there were no difference between A-male > and A-female but A tended to be larger than the other groups, then > including A-male and not A-female would create a confound making males > look bigger than females. > > 2. Does mri_glmfit have a limit to the number of subjects it can run > > with? If I have say upwards of a few thousand subjects, will this be > > possible to run/how long would that take? > I don't think it has a limit. > > > > Thanks for your help! > > > > Regards > > Yann > > > > > > _______________________________________________ > > Freesurfer mailing list > > Freesurfer@nmr.mgh.harvard.edu > <mailto:Freesurfer@nmr.mgh.harvard.edu> > > https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer > <https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer> > > End of Freesurfer Digest, Vol 161, Issue 17 > ******************************************* > > -- Douglas N. Greve, Ph.D. MGH-NMR Center gr...@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/ _______________________________________________ Freesurfer mailing list 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.
