70. Example 12.7 presented the residuals from a simple linear regression of moisture content y on ltration 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 ei *  ei/s for i  1, . . . , n, or are the ei * s not close to being proportional to the ei s?

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