why not a continuous model? what model do you want to use?
Xie, Hong wrote:
Thanks a lot. This scrip seemly describes F-test or T-test. In my study, I want to analyze the correlationship between patient's cortical thickness and pain scale (from 0 to 6). After I create data table. Qdec automatically put pain scale into continuous variable category. Actually, pain scale is ordinal variable, not continuous variable. Different correlation model should be used. How should I do it by qdec? I very appreciate your help. Hong Xie
*From:* Douglas N Greve [mailto:greve@nmr.mgh.harvard.edu] *Sent:* Mon 1/12/2009 3:11 PM *To:* Xie, Hong *Cc:* freesurfer@nmr.mgh.harvard.edu *Subject:* Re: [Freesurfer] Qdec correlation analyses
Not with QDEC, but you can write your own FSGD, See
https://surfer.nmr.mgh.harvard.edu/fswiki/FsgdExamples
Xie, Hong wrote:
Hello, Thank you for answering me. I searched mailing list and read this answer email: /I see that group.levels has four levels. Unfortunately, right now qdec only supports two levels for a discrete factor. One the features in the works is to increase this./ /Nick Schmansky Wed, 27 Feb 2008 11:08:10 -0800/ Is this question still here? I have a five levels discrete factor. Can I run correlation statistic by Qdec? Thanks again Hong Xie
*From:* Douglas N Greve [mailto:greve@nmr.mgh.harvard.edu] *Sent:* Thu 1/8/2009 4:40 PM *To:* Xie, Hong *Cc:* freesurfer@nmr.mgh.harvard.edu *Subject:* Re: [Freesurfer] Qdec correlation analyses
It has to be interpreted as a continuous variable. The test is done using a t-test inside the glm. This reduces to a Pearson if there is only one variable and no intercept (which it is not).
doug
Xie, Hong wrote:
Hello, freesurfer group,
I have run qdec for comparing thickness between two groups. When qdec does a correlation analyses for thickness versus a second variable: 1) Does the second variable have to be a continuous interval variable or 2) can the second variable be an ordinal variable with more than 2 levels? In the case of the correlation between two continuous variable, is the test a Pearson correlation? If 2) is possible, is the correlation a Spearman correlation?
Thank for your help,
Hong Xie
Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer