Example 12.6 presented the residuals from a simple linear regression of moisture content y on filtration rate x.

a. Plot the residuals against x. Does the resulting plot suggest that a straight-line regression function is a reasonable choice of model? Explain your reasoning.

b. Using s
.665, compute the values of the standardized residuals. Is e*i
ei /s for i
1, . . . , n, or are the e*is not close to being proportional to the eis?

c. Plot the standardized residuals against x. Does the plot differ significantly in general appearance from the plot of part (a)?