Hi all, I have run a (glm) analysis where the dependent variable is the gender (family=binomial) and the predictors are percentages. I get a warning saying "fitted probabilities numerically 0 or 1 occurred" that is indicating that quasi-separation or separation is occurring. This makes sense given that one of these predictors have a very influential effect that is depending on a specific threshold separating these effects, in other words in my analysis one of these variables predicts males about the 80% of times when its values are less or equal to zero and females about the 80% when its values are greater than zero. I have been looking at other posts about this but I haven’t understood how I should act when the separation (or quasi separation) is not a statistical artifact but it is something real. As suggested in http://r.789695.n4.nabble.com/OT-quasi-separation-in-a-logistic-GLM-td875726.html#a3850331 http://r.789695.n4.nabble.com/OT-quasi-separation-in-a-logistic-GLM-td875726.html#a3850331 (the last post is mine) I tried to use brglm procedure that uses a penalized maximum likelihood but it made no difference.
What would you do if you were in my shoes? Thanks in advance for any help. Simone -- View this message in context: http://r.789695.n4.nabble.com/binomial-GLM-quasi-separation-tp3901687p3901687.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
