Problem 10.20

(This is a continuation of the fuel efficiency Example 10.2.) The ANOVA table for the Model (Y = gpm|X = weight) follows. Analysis of Variance Sum of Mean Source DF Squares Square F Value Prob>F Model 1 0.59506 0.59506 23.916 0.0006 Error 10 0.24881 0.02488 C Total 11 0.84387 Root MSE 0.15774 R-square 0.7052 Parameter Estimates Parameter Standard T for H0: Variable Estimate Error Parameter=0 Prob > |T| INTERCEP 2.179754 0.29867670 7.298 0.0001 SLOPE 0.449247 0.09186264 4.890 0.0006

(a) Using the computer output displayed in the ANOVA table (and the result that x = 3.21, Sxx = 2.95), construct 95% confidence intervals for β0 and β1.

(b) Compute a 95% confidence interval for the mean gpm of an automobile that weighs 2530 lbs.

(c) Compute a 95% prediction interval for the gpm of a 1992 Escort that also weighs 2530 lbs. Compare the predicted value to the actual value, which is 3.34 gpm.