On Sat, 15 Sep 2007, Wensui Liu wrote: > Dear Listers, > I have a general statistical question. Are hurdle logit-poisson model > and posson model nested?
No, I don't think so. The logit hurdle is equivalent to a geometric hurdle (i.e., logit and right-censored geometric distribution imply the same likelihood and thus the same estimates), so a hurdle logit-geometric model is nested withing a geometric model. If you want a model nested in poisson, you can use a hurdle poisson-poisson model, i.e., a right-censored poisson for the zero hurdle and a left-truncated poisson for the counts. A test for presence of the hurdle is then a test that all parameters are equal. The hurdle() function in "pscl" can fit these models and hurdletest() can test for the presence of the hurdle (given that the same distribution has been used for the zero hurdle and the counts). Best, Z > Thank you so much? > > ______________________________________________ > 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. > > ______________________________________________ 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.
