Here are some diagnostic plots for the final exam data from Exercise 13. These were generated by a computer package and may look different from the plots generated by the packages you use. (In particular, note that the axes of the Normal probability plot are swapped relative to the plots we've made in the text. We only care about the pattern of this plot, so it shouldn't affect your interpretation.) Examine these plots and discuss whether the assumptions and conditions for the multiple regressions seem reasonable.
In Exercise 13

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Dependent variable is Final s# 13.46 R-Sq:e 77.7% R-Sq(adj)--74.1% Predictor Coeff SE(Coeff) t P-value Intercept -6.72 Testl Test2 Test3 Analysis of Variance Source Regression 3 11961.8 3987.3 22.02 <0.0001 Error Total 14.00 -0.48 0.636 0.2560 0.2274 1.13 0.274 0.3912 0.2198 1.78 0.091 0.9015 0.2086 4.32 <0.0001 DF MS P-value 19 3440.8 181.1 22 15402.6 Residuals vs. the Fitted Values Response is Final) 20 T -20 t 50 60 70 80 90 100 110 120 130 140 150 Fitted Value Normal Probability Plot of the Residuals (Response is Final) 8 -1 -20 -10 10 20 Residual (points) Histogram of the Residuals (Response is Final) 4 -20-15 -10 -5 0 5 10 15 20 Residuals (points)