10.19 Refer to the toxicity study with data summarized in Table 10.12. Collapsing the ordinal response to binary in terms of whether with data summarized in the outcome is normal, consider logistic models as a linear function of the dose level.

a. Does the ordinary binomial GLM show evidence of overdispersion?

b. Fit the logistic model using a GEE approach with exchangeable working correlation among fetuses in the same litter. Interpret and compare with results in (a).

c. Fit the logistic GLMM after adding a litter-specific normal random effect.

Interpret and compare with previous results.