On Tue, 12 Aug 2003, Martin Hoyle wrote: > I'm trying to use the command "glm.nb" in library(MASS) to test for a > significant difference in the aggregation parameter "theta" between the > three levels of a factor.
You cannot in general do that: each fit has one theta parameter. You may be able to do three separate fits, one for each level, and sum the loglikelihoods and do a likelihood ratio test by hand. (It depends exactly what the model you are using is.) -- Brian D. Ripley, [EMAIL PROTECTED] Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595 ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help
