Refer to Table 7.1 on high school students’ use of alcohol, cigarettes, and marijuana.

Consider the data as matched triplets.

a. Construct the marginal distribution for each substance. Specify a marginal model that can compare them and explain how to interpret its parameters. State the hypothesis of marginal homogeneity in terms of model parameters.

b. Specify a corresponding subject-specific model. Explain how parameter interpretation differs from the marginal model.

c. Construct a data file to fit the marginal model. (Hint: You could mimic the Abortion data file, ignoring gender.) Use GEE methods to fit the model and to test the hypothesis of marginal homogeneity.