9,5A Generalization We can extend our model to include more than on quantitative variable and more than two qualitative variables, but the number of dummies for each qualitative variable is one less than the number of categories of that variable9.5 A Generalization We can extend our model to include more than on quantitative variable and more than two qualitative variables, but the number of dummies for each qualitative variable is one less than the number of categories of that variable