Problem 11.9 Refer to the ground water quality data set of Problem 10.12.

(a) Fit the multiple linear regression Model (Y = TDS | X1 = SEC, X2 = SiO2) and state the estimated regression function.

(b) Estimate the change in the total dissolved solids (TDS) when the specific electrical con[1]ductivity (SEC) is increased by 100 ms/cm and the amount of silica (SiO2) is increased by 5.

(c) What is the fitted value and residual corresponding to X1 = 841 and X2 = 48?

(d) Compute the ANOVA table, R2, and the adjusted R-square.

(e) Use the partial F test to decide if X2 should be dropped from the regression model.