Hi Lizanne, I do not use SPSS so I cannot comment on which model is equivalent. BTW, if you can save the design an contrast matrices in text form from SPSS, then you can feed them into mri_glmfit. I'm cc'ing Steve Hodge who has been working on mapping R design matrices to FS on the chance that he might have some insight. doug
On 03/25/2014 06:04 AM, L. Schweren wrote: > > // > > /Dear FreeSurfer experts, / > > // > > /Thank you for your fast reply. We are extracting cortical thickness > values for statistical sub-analyses in SPSS (due to corrections > required with regard to family relatedness within the data); therefore > we want to be a 100% certain that the statistical model we use in SPSS > is identical to the model used by mri_glmfit. Can you confirm that, > out of the multiple linear regression types listed below, mri_glmfit > makes use of the Direct (or Standard) regression model?/ > > // > > *Type* > > > > *Characteristics* > > Direct (or Standard) > > > > ·All IVs are entered simultaneously > > Hierarchical > > > > ·IVs are entered in steps, i.e., some before others > > ·Interpret: /R/^2 change, /F/ change > > Forward > > > > ·The software enters IVs one by one until there are no more > significant IVs to be entered > > Backward > > > > ·The software removes IVs one to one until there are no more > non-significant IVs to removed > > Stepwise > > > > ·A combination of Forward and Backward MLR > > // > > /Thank you again for your help, / > > // > > /Best wishes, / > > /Lizanne/ > > Date: Wed, 12 Mar 2014 11:04:00 -0400 > > From: Douglas Greve <gr...@nmr.mgh.harvard.edu> > > Subject: Re: [Freesurfer] glmfit with correlated covariates > > To: freesurfer@nmr.mgh.harvard.edu > > Message-ID: <53207760.8010...@nmr.mgh.harvard.edu> > > Content-Type: text/plain; charset="iso-8859-1" > > It is just a standard multiple regression analysis where all regressors > > are fit simultaneously. One weight does not include that of another > weight. > > doug > > On 3/12/14 5:16 AM, L. Schweren wrote: > > > > > > Dear FreeSurfer experts, > > > > > > I am attempting to disentangle the effects of different features of > > > pharmacological treatment on cortical thickness. > > > > > > I am running glmfit from the commandline, with multiple covariates > > > (a.o. Z_Age, Z_TreatmentDuration and Z_StartAge) in the fsgd-file. > > > These covariates are correlated up to approximately 0.6 , which to my > > > understanding is not ideal yet not inducing collinearity. Running > > > glmfit, I do not get any errors such as ill-designed matrix or so. > > > > > > My question regards the way the different regression weights are > > > calculated in each voxel. If I test the variance in CT of voxel A > > > explained by for example TreatmentDuration, and part of the variance > > > in voxel A is explained by both TreatmentDuration and StartAge, will > > > the regression weigth of TreatmentDuration than include the part that > > > is also explained by StartAge? Or are all other covariates first > > > "regressed out" of the variance, such that the variable I test can > > > only explain the variance that was not explained by any of the other > > > covariates? > > > > > > Thank you very much, your help is very much appreciated! > > > > > > Best wishes, > > > > > > Lizanne > > > > > > > > > > > > _______________________________________________ > > > Freesurfer mailing list > > > Freesurfer@nmr.mgh.harvard.edu > > > https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer > > > > _______________________________________________ > 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: 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.
