[R] GLM model simplification

Martin Hoyle plxmh at nottingham.ac.uk
Tue Apr 15 18:47:57 CEST 2003

Hello R Users,

I have the GLMs:

model1 <- glm (response ~ explanatory * block, poisson)
model2 <- glm (response ~ explanatory + block, poisson)
anova(model1, model2, test="Chi")

and I find that the interaction is significant.
I am interested in the main effect of "explanatory". However, I am advised that model simplification should stop when a higher order term is found to be significant (here, the interaction).
I imagine that I should do;

model3 <- glm (response ~ block, poisson)
anova(model2, model3, test="Chi")

to test for the significance of the main effect of "explanatory". Am I allowed to do this, even though the interaction is significant?

Thanks for your attention,

Martin Hoyle,
School of Life and Environmental Sciences,
University of Nottingham,
University Park,
NG7 2RD,
Webpage: http://myprofile.cos.com/martinhoyle

More information about the R-help mailing list