You have done the right thing, but you need to know a little more. When QDEC says "mean thickness" it really means the thickness at age=0, so it is extrapolating the results back to age=0. Since you have a covariate and you are using DODS, you have to specify an age at which to do the test (you can't actually test the means with the covariate). If you demean the covariate, you will test it at age=mean age. Alternatively, you can use DOSS to model one slope across both groups and test for the difference in intercept (which will be age-independent with DOSS).

doug

johanna feiler wrote:

Dear Freesurfers,

in my qdec analysis I want to compare my patients group with a control group. The analysis should be corrected for age effects, so I used group as discrete factor and age as covariate. If I choose „Does the average thickness differ between the two groups“, how can I interpretate a significant result in a certain region? Does it mean: „The mean thickness in this region differs between both groups significantly, correcting for age effects“? I got some highly significant results, however the groups' means don't seem to differ that much, however, the groups' trends seem to be quite different. So which statistical test is implemented ins qdec?

Any help will be appreciated!

Thanks a lot, Johanna Feiler ___________________________________________________________ GRATIS für alle WEB.DE-Nutzer: Die maxdome Movie-FLAT! Jetzt freischalten unter http://movieflat.web.de

---

Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer