"Ronaldo Reis Jr." <[EMAIL PROTECTED]> writes:
> Hi,
>
> I make an analysis and depending of the order of the variables, the
> significance change, look.
>
> m1 <- glm((infec/ntot)~idade+sexo+peso,family=binomial,weights=ntot)
> > anova(m1,test="F")
> Analysis of Deviance Table
>
> Model: binomial, link: logit
>
> Response: (infec/ntot)
>
> Terms added sequentially (first to last)
>
...
>
> Why this?
Because terms are added sequentially. Adding a variable to a model
means different things depending on what else is in the model. Most
textbooks on regression will explain this.
> How the best method to select the model (with idade or without idade)? AIC?
I'd suggest looking at a direct comparison:
m1 <- glm((infec/ntot)~idade+sexo+peso,family=binomial,weights=ntot)
m2 <- glm((infec/ntot)~sexo+peso,family=binomial,weights=ntot)
anova(m1,m2,test="F")
-p
--
O__ ---- Peter Dalgaard Blegdamsvej 3
c/ /'_ --- Dept. of Biostatistics 2200 Cph. N
(*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918
~~~~~~~~~~ - ([EMAIL PROTECTED]) FAX: (+45) 35327907
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