Dear Amanda, According to "Statistical Computing" by Crawley, p545, you can deal with overdispersion by any one of 3 ways; 1: Carry out significance tests using "F" rather than "Chi" in the anova function for comparison of deviances, 2: Use quasipoisson, and specify a variance function, or, 3: Use negative binomial error (see library(MASS), glm.nb). To answer the second part of your qu, if you do summary(model), you will get the estimate and s.e. of the log transform of your response variable (log is the default link). Cheers, Martin. Martin Hoyle, School of Life and Environmental Sciences, University of Nottingham, University Park, Nottingham, NG7 2RD, UK Webpage: http://myprofile.cos.com/martinhoyle
Amanda Phipps <genepi51 at yahoo.com> 05/01/03 06:04am >>>
I am fitting a poisson model and it appears to have overdispersion. I am interested in using the quasipoisson family (with the glm command). Will this account for the overdispersion in the model? Is there an additional method for accounting for a dispersion parameter not equal to 1 (with the glm command)? And after fitting the model, how to I obtain the fitted values and their respective standard errors? Thank you- Sarah Watson ______________________________________________ R-help at stat.math.ethz.ch mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help