[R] Chi square value of anova(binomialglmnull, binomglmmod, test="Chisq")

[David Winsemius]

On Jun 4, 2012, at 7:00 AM, lincoln wrote:

> Hi all,
>
> I have done a backward stepwise selection on a full binomial GLM  
> where the
> response variable is gender.
> At the end of the selection I have found one model with only one  
> explanatory
> variable (cohort, factor variable with 10 levels).
>
> I want to test the significance of the variable "cohort" that, I  
> believe, is
> the same as the significance of this selected model:
>
>> anova(mod4,update(mod4,~.-cohort),test="Chisq")
> Analysis of Deviance Table
>
> Model 1: site ~ cohort
> Model 2: site ~ 1
>  Resid. Df Resid. Dev Df Deviance P(>|Chi|)
> 1       993     1283.7
> 2      1002     1368.2 -9  -84.554 2.002e-14 ***
> ---
> Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
>
> My question is:
> When I report this result, I would say /"cohorts were unevenly  
> distributed
> between sites ( Chi2=84.5, df=9, p < 0.001)"/, is that correct? is  
> the Chi2
> value the difference of deviance between model with cohort effect  
> and null
> model?

I thought you said the response variable was gender? It seems to be  
'site' in these two models. Maybe you should give us some more  
information about how you constructed 'mod4'?

-- 

David Winsemius, MD
West Hartford, CT