Chapter 8, Problem 12E

(a)

To determine

To explain what each of the residual plots below indicates about the appropriateness of the linear model that was fit to the data.

Explanation of Solution

In the residual plot in part (a), we can say that the points in the residual plot is in U-shaped curve, that is, the points are going downwards and then upwards. Thus, the curved pattern shown in the residual plot indicates that a linear model is not an accurate model for the data. The relationship is not linear.

(b)

To determine

To explain what each of the residual plots below indicates about the appropriateness of the linear model that was fit to the data.

Explanation of Solution

In the residual plot shown in part (b), we can say that the points in the residual plot is in constant direction and then as we move ahead the pattern of points seems to be spread out. Thus, we can say that the fanned pattern indicates heteroscedastic data. The model's predicting power increases as the value of the explanatory variable increases.

(c)

To determine

To explain what each of the residual plots below indicates about the appropriateness of the linear model that was fit to the data.

Explanation of Solution

In the residual plot shown in the part (c), we can say that the points in the residual plot shows no pattern in the plot as the points are spread out in the whole residual plot. Thus, we can say that this is the the scattering residual plot indicates that the linear model is appropriate.