Goodness of fit test for modeling of count data
Poisson and negative binomial regression are used for modeling count data. This command tests the deviance against the degrees of freedom in the model thus determining whether there is overdispersion.
poisgof(model)
model |
A Poisson or negative binomial model |
To test the significance of overdispersion of the errors of a Poisson or negative binomial model, the deviance is tested against degrees of freedom using chi-squared distribution. A low P value indicates significant overdispersion.
Virasakdi Chongsuvivatwong <cvirasak@medicine.psu.ac.th>
‘glm’
library(MASS) quine.pois <- glm(Days ~ Sex/(Age + Eth*Lrn), data = quine, family=poisson) poisgof(quine.pois) quine.nb1 <- glm.nb(Days ~ Sex/(Age + Eth*Lrn), data = quine) poisgof(quine.nb1)
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