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

lincoln miseno77 at hotmail.com
Mon Jun 4 13:00:52 CEST 2012


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?

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