Hi, Thanks for the reference and explanation of the subtle statistical inferences. It was very useful.
You are right in what i am trying to show (c- controls, p1 to p4 patients with varying levels of endogenous factor) which is that when patients are subdivided into levels of endogenous factor there is correlation with the changes seen in dependent variables compared to controls. So far, C v whole P gp - differences seen in plausible areas. C v P1 (greatest endo factor) subgp - no differences C v P4 subgp (lowest endo factor) - differences seen in plausible areas. Given that it is not valid to compare c v p1 and c v p4 (and p1 v p4 shows nothing) is the following valid - perhaps it is similar to what you proposed: Consider c and p1 to p4 as one group of subjects (theoretically the only difference between subjects being level of endogenous factor) but assign each subject a variable which represents level of endoenous factor (c - 1 p1 - 2 p3 - 4 p4 - 5) - then run glm looking for correlation between endogenous factor and dependent variable. Is this very different to what you suggested and any less valid ? Thanks. M _______________________________________________ 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.
