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
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