Yes, let's say you have 4 groups (eg, gender and sequence) and one covariate (BDI score). If you use a DODS model, then you will have 8 regressors (4 intercepts and 4 slopes). To test for an effect of covariate regressing out the group, then you would have
[0 0 0 0 .25 .25 .25 .25] The +0.25 computes the mean slope across all groups (note you could also just use all 1s, you will get the same p-value). On 03/09/2018 01:43 PM, k.ohmst...@stud.uni-heidelberg.de wrote: > Hi Douglas, > > thanks for the advice. > > I have one more question: I want to find correlations of the lGI and > the respective psychometric measurement, regressing out the effect of > gender, sequence and the other covariates. > I just had a look at the examples of FSGDs containing two factors with > two levels each and as far as I understand it, it is only possible to > compare two of the groups or to find an interaction between groups and > covariates. > > Is it at all possible to find out how the lGI is correlated to one of > my covariates, i.e. higher values of Beck's Depression Inventory > correlate with higher/lower values of the lGI, when regressing out the > other factors? If yes, how do I build the contrast file to do so > correctly? I am stuck here. > > Thank you for the time and effort! > > > Best regards > > Kai > > Zitat von Douglas Greve <dgr...@mgh.harvard.edu>: > >> Hi Kai, please remember to post to the list. Your FSGD file is not >> quite right. Gender is a discrete variable and should be represented by >> two groups not as a covariate. If Sequence is discrete, then you need >> four groups (Gender by Sequence). >> >> doug >> >> >> On 3/9/18 3:20 AM, k.ohmst...@stud.uni-heidelberg.de wrote: >>> Dear Douglas, >>> >>> the fsgd file I used is attached. Thank you for your help! >>> >>> >>> Best regards >>> >>> Kai >>> >>> Zitat von "Douglas N. Greve" <dgr...@mgh.harvard.edu>: >>> >>>> can you send your fsgd file so that I have a better idea of what >>>> you are >>>> mentioning? >>>> >>>> >>>> On 03/08/2018 08:39 AM, k.ohmst...@stud.uni-heidelberg.de wrote: >>>>> Dear all, >>>>> >>>>> I am trying to correlate psychometric measurements and the local >>>>> Gyrification Index. >>>>> To do so, I use the FreeSurfer pipeline to calculate the lGI and then >>>>> PALM, following the advice in this thread >>>>> (https://mail.nmr.mgh.harvard.edu/pipermail//freesurfer/2017-March/050703.html). >>>>> >>>>> All my subjects are part of the same group, so I used a FSGD with >>>>> the >>>>> group "main" to create the design matrix and mask for my data that >>>>> are >>>>> required by PALM. >>>>> Having a closer look at the design matrix that was created, I found >>>>> that there was a variable for the group that was the same for all my >>>>> patients. As it is the same for all patients, I thought >>>>> eliminating it >>>>> would not be a problem. But after re-running PALM without it, there >>>>> were huge differences in my results and effects were notably larger >>>>> and more significant. >>>>> >>>>> Do any of you have any experience which option is best in this case? >>>>> Is it a valid choice to eliminate the variable for the group, as >>>>> it is >>>>> the same for each patient anyway? >>>>> >>>>> Furthermore, would you recommend centering for the design matrix? I >>>>> found that this can have an impact, but I am lost on in which >>>>> cases it >>>>> should be done and in which it shouldn't. >>>>> >>>>> >>>>> Thank you for your help! >>>>> >>>>> >>>>> Best regards >>>>> >>>>> Kai Ohmstedt >>>>> >>>>> >>>>> _______________________________________________ >>>>> 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 >>>> >>>> >>>> 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
