Yes, that looks fine. The only other thing to decide is whether to use DODS (different offset different slope) or DOSS (different offset same slope). The default is DODS, but if you don't think that there is an age-by-group interaction, then you can get more power using DOSS. If you use DODS, then you should probably de-mean the ages (ie, subtract the grand mean age over all subjects from the age of each individual).
doug Roser Sala wrote: > Hi, > > We are doing a group analysis using qdec with two groups, and we would > like to include gender and age as covariates. > > Which is the best option in order to perform a simple t-test > (group1>group2 and group2>group1) and including the two covariates? > (we would like them to have 'zero' weighting in the contrast matrix) > > We realized that if we include 'age' as a continous factor in the > dialog, qdec is performing rather an interaction analysis than a > covariate. > > So, would it be ok to include group and gender as fixed factors and > age as nuisance, and then select the output as 'Does the average > thickness accounting for gender differ between group1 and group2' (age > as nuisance variable)? > By checking all the possibilities this seemed the best option for us, > but we would like to get a confirmation that we are doing it right. > > Many thanks > > Roser > ------------------------------------------------------------------------ > > _______________________________________________ > 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 _______________________________________________ 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.
