Chapter 7
Polynomial Regression Models
7.1 Yes there are potential problems since the correlation (x, x2) = .995
7.2 a. 
= 1.63 − 1.23x + 1.49x2.
= 1.63 − 1.23x + 1.49x2.b. F = 1.86 × 106 with p = 0.000 which is significant.
c. 
which is significant.
which is significant.d. Since it is a quadratic model, there can be potential hazards in extrapolating.
7.3 There is a problem with normality. The residuals seem to show that the model is adequate.
7.4 a. = −4.5 + 1.38x + 1.47x2.
= −4.5 + 1.38x + 1.47x2.b. F = 1044.99 with p = 0.000 which is significant.
c. F = 48.7 with p = 0.001 which is indicates lack of fit.
d. 
which is significant and indicates the term cannot be deleted.
which is significant and indicates the term cannot be deleted.7.5 There is an outlier which affects the normality and the residual plot which shows the model is not adequate.
7.6 a. = 3025 − 194x1 − 6.1x2 + 3.63x21 + 1.15x22 − 1.33x1x2.
= 3025 − 194x1 − 6.1x2 + 3.63x21 + 1.15x22 − 1.33x1x2.b.
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