73. The accompanying data on x  true density

(kg/mm3) and y  moisture content (% d.b.) was read from a plot in the article Physical Properties of Cumin Seed (J. Agric. Engrg. Res., 1996: 93—98).

x 7.0 9.3 13.2 16.3 19.1 22.0 y 1046 1065 1094 1117 1130 1135 The equation of the least squares line is y1008.14

6.19268x (this differs very slightly from the equation given in the article); s  7.265 and r 2  .968.

a. Carry out a test of model utility and comment.

b. Compute the values of the residuals and plot the residuals against x. Does the plot suggest that a linear regression function is inappropriate?

c. Compute the values of the standardized residuals and plot them against x. Are there any unusually large (positive or negative) standardized residuals?

Does this plot give the same message as the plot of part

(b) regarding the appropriateness of a linear regression function?