a.-d. Answer the same questions as in parts (a) through (d) in Problem 1 regarding an analysis of covariance designed to control for both AGE and QUET. (AGE = 53.250.) Use the results from Problem 9 in Chapter 12.
e. Is it necessary to control for both AGE and QUET as opposed to controlling just one of the two covariates?
In Problem 1
a. State the appropriate ANACOVA regression model to use for comparing the mean blood pressures in the two smoking categories, controlling for QUET.
b. Determine the adjusted SBP means for smokers and nonsmokers. Compare these values to the unadjusted mean values
SBP(smokers) = 147.823 and SBP( nonsmokers) = 140.800
c. Test whether the true adjusted mean blood pressures in the two groups are equal. State the null hypothesis in terms of the regression coefficients in the ANACOVA model given in part (a).
d. Obtain a 95% confidence interval for the true difference in adjusted SBP means.

Regression of SBP on QUET and SMK ANALYSIS OF VARIANCE Sum of DFI Squares Mean Square F Value Pr>F Source Model Error Corrected Total 4889.82570 1629.94190 29.71 $.0001 28 1536.14305 54.86225 3 64259687 Root MSE Dependent Mean Coeff Var 7 40691 144.53125 5.12478 0.7609 R-Square Adj R-Sq 0.7353 PARAMETER ESTIMATES Parameter Standard VariableDF Intercept SMK AGE QUET Error t Value Pr>t Type I SS 4.19 0.0003 3.74 0.0008 45.10319 10.76488 668457 393.09816 3.75 0.0008 4296.58607 200 14147 9.94557 2.65606 0.32382 4.49868 191 121271 032382 18.59245 4,49868 11 0.0664 2