Use the computer output shown next to compare the separate regressions of SBP on AGE and QUET for smokers and nonsmokers (based on the data from Problem 2 in Chapter 5), as follows.
a. State the appropriate regression model, simultaneously incorporating equations for both smokers and nonsmokers.
b. Determine the fitted regression equations for smokers and nonsmokers separately, using the fitted regression model.
c. Test for parallelism of the two models, stating the null hypothesis in terms of appropriate regression coefficients.
d. Test for coincidence of the two models, stating the null hypothesis in terms of regression coefficients.