On May 26, 3:17 pm, dfis...@CSULB.EDU ("Dennis G. Fisher, Ph.D.") wrote: > Peter, > MV is ever use of both Methamphetamine and Viagra. The data actually > make sense. The question is what to do about it? > Thanks. > Dennis > > Peter Flom wrote: > > Hi Dennis > > > well, unless I am reading this wrong (it got formatted oddly) you only have 2 people in one of the cells....so, things are going to be weird! One could say that ANY model is overfit, because a single noise variable will suffice to put 1 person in the right cell > > > What is MV? > > > Peter > > > -----Original Message----- > > >> From: "Dennis G. Fisher, Ph.D." <dfis...@CSULB.EDU> > >> Sent: May 26, 2007 1:58 PM > >> To: S...@LISTSERV.UGA.EDU > >> Subject: logistic regression wierdness > > >> We are trying to construct a logistic regression model. When we put > >> ever use of marijuana in the model, we get an odds ratio of 5.414 and > >> the model seems to fit. We still get another 10 variables that seem to > >> be OK. Usually when this kind of thing happens, I figure it is either > >> dirty data or we coded something wrong, but this time I think it is > >> real. The 2 x 2 table is > >> Marijuana > >> No Yes > > >> MV No 194 443 > > >> Yes 2 165 > > >> This is almost seems like a a quasi complete separation, but it really > >> is not I don't think. I am going to feel really strange trying to > >> present a model with an OR this big, but I cannot figure out why I > >> should take it out of the model. What would you do? Thanks. > > >> Dennis Fisher, Ph.D. > >> Center for Behavioral Research and Services > >> California State University, Long Beach

Treat it as a single three category variable (none, marijuana, marijuana+meth+viagra) with two weirdos?

-bwg