Re: [R] Unrealistic dispersion parameter for quasibinomial

2010-03-04 Thread Etienne Bellemare Racine
Ben Bolker wrote : The dispersion parameter depends on the Pearson residuals, not the deviance residuals (i.e., scaled by expected variance). I haven't checked into this in great detail, but the Pearson residual of your first data set is huge, probably because the fitted value is tiny (and hence

Re: [R] Unrealistic dispersion parameter for quasibinomial

2009-03-04 Thread Prof Brian Ripley
For the record residuals(model) 1 2 3 4 5 5.55860143 -0.00073852 2.49255235 -1.41987341 -0.00042425 6 7 8 -0.94389158 2.72987046 -1.15760836 residuals(model, "pearson") 1 2 3

Re: [R] Unrealistic dispersion parameter for quasibinomial

2009-03-03 Thread Ben Bolker
Menelaos Stavrinides gmail.com> writes: > > I am running a binomial glm with response variable the no of mites of two > species y->cbind(mitea,miteb) against two continuous variables (temperature > and predatory mites) - see below. My model shows overdispersion as the > residual deviance is 48.8

[R] Unrealistic dispersion parameter for quasibinomial

2009-03-02 Thread Menelaos Stavrinides
I am running a binomial glm with response variable the no of mites of two species y->cbind(mitea,miteb) against two continuous variables (temperature and predatory mites) - see below. My model shows overdispersion as the residual deviance is 48.81 on 5 degrees of freedom. If I use quasibinomial t