Hi Doug, There are approaches/methods available for permutation testing with non-orthogonal design matrices -- see for example the documentation for FSL's randomise and the references cited therein.
cheers, -MH -- Michael Harms, Ph.D. ----------------------------------------------------------- Conte Center for the Neuroscience of Mental Disorders Washington University School of Medicine Department of Psychiatry, Box 8134 660 South Euclid Ave. Tel: 314-747-6173 St. Louis, MO 63110 Email: mha...@wustl.edu On 4/4/13 11:16 AM, "Douglas N Greve" <gr...@nmr.mgh.harvard.edu> wrote: >Correct, you cannot do a permutation test with continuous variables (or >with any non-orthogonal design matrix). If you use the --perm-force, it >will do the permutation test as normal (by randomly swapping the rows), >but technically the test is not legal. Having said that, I suspect that >LOTS of people do exactly that. >doug > > > >On 04/04/2013 10:03 AM, Gabriel Gonzalez Escamilla wrote: >> >> Dear Freesurfer experts, >> >> >> I'm having troubles when setting a permutation test, I'm making group >> comparisons, but I'm introducing the Age, and cortical thickness as >> niusance variables (as previously recommended). >> >> It seems that permutations only work for orthogonal matrices, does >> this means that I cannot set any niusance variable? >> >> >> If so, this is telling me that I can run the command with the flag >> "--perm-force", and I'm wondering, which would be the implications of >> force to run the permutations with niusance variables? >> >> >> Many thanks in advance, >> Gabriel >> >> >> _______________________________________________ >> Freesurfer mailing list >> Freesurfer@nmr.mgh.harvard.edu >> https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer > >-- >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: 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. _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
