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:gr...@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
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