Hi Mahinda, make sure to include previous correspondence so that we know what previous the previous suggestions are. Your analysis sounds technically correct if you can justify the 1, 2, and 5 values for the covariate. This design will give you a little more power.
doug On 11/27/2012 01:28 PM, Mahinda Yogarajah wrote: > 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 > > -- 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 Outgoing: ftp://surfer.nmr.mgh.harvard.edu/transfer/outgoing/flat/greve/ _______________________________________________ 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.
