[R] F tests for glms with binomial error
tr217@cam.ac.uk
tr217 at cam.ac.uk
Wed Apr 4 13:18:39 CEST 2001
Hi, can anyone help with this:
I am trying to analyse some data in the form of proportions with the glm
function in R and S-plus. When comparing different models with an F test,
I get different results from R and S-plus. Here's an example (there are
two factors and an interaction in the full model
"glm1<-glm(resp~time*set,family=binomial"):
In R, entering "anova(glm1)" I get this:
DF Deviance Resid. DF Resid. Deviance F Pr(>F)
NULL 51 213.13
time 1 1.403 50 211.727 1.4032 0.23618
set 6 98.527 44 113.2 16.4211 <2e-16***
time:set 6 13.659 38 99.541 2.2765 0.03368*
But in S-plus, I get this:
DF Deviance Resid. DF Resid. Deviance F Pr(>F)
NULL 51 213.13
time 1 1.403 50 211.727 0.6749 0.4165
set 6 98.527 44 113.2 7.8986 0.000015***
time:set 6 13.659 38 99.541 1.0950 0.3831
Everything is the same, except for the F ratios. Does anyone know why (as
you can see it makes quite a difference to the significance of the
interaction term)?
Thanks,
Tom Reader.
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