The text website contains an expanded version (file Drugs3.dat) of the student substance use data of Table 7.3 that also has each subject’s G = gender

(1 = female, 2 = male) and R = race (1 = white, 2 = other). It is sensible to treat G and R as explanatory variables. Explain why any loglinear model for the data should include the GR two-factor term. Use a model-building process to select a model for these data. Interpret the estimated conditional associations.