Consider the data in Exercise 11-7 on y green liquor Na2S concentration and x paper machine production.

Suppose that a 14th sample point is added to the original data, where y14 59 and x14 855.

(a) Prepare a scatter diagram of y versus x. Fit the simple linear regression model to all 14 observations.

(b) Test for significance of regression with  0.05.

(c) Estimate 2 for this model.

(d) Compare the estimate of 2 obtained in part

(c) above with the estimate of 2 obtained from the original 13 points.

Which estimate is larger and why?

(e) Compute the residuals for this model. Does the value of e14 appear unusual?

(f) Prepare and interpret a normal probability plot of the residuals.

(g) Plot the residuals versus and versus x. Comment on these graphs.