Dear all,
I performed regression logistic analysis and I want to test if the observed
probabilities of the event on a subset of my data are equivalent to the
expected probabilities using the result of a fit based on another subset of the
data.
My code is below but I am not sure of the validity of my method. Does anyone
could help me?
Cheers,
Roch
My SPLUS code (I am using SPLUS 6.2 for Windows):
First I fit the model on the validation group (subset=(group==1)):
fit1 <- glm(event ~ x1, subset=(group==1), family=binomial, data=MyData)
Then I obtain the individuals predictions:
exp.proba <- predict(fit1, data.frame(age=MyData$x1), type='response')
I add "exp.proba" to my dataset.
I fit the model on the test group (subset=(group==0)) using logit(exp.proba) on
the offset:
fit2 <- glm(event ~ 1 + offset(log(exp.proba/(1-exp.proba))),
subset=(group==0), family=binomial, data=MyData)
summary(fit2)
_____________________________________________________
Roch GIORGI, MD, PhD
Service de Santé Publique et d'Information Médicale
Hôpital de la Timone
264, rue St Pierre
13385 Marseille cedex 5
Tel: +33 (0)491 384 949
Fax: +33 (0)491 385 749
email: roch.giorgi@ap-hm.fr
Web: http://cybertim.timone.univ-mrs.fr/
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