Consider the data in Exercise 11-8 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 a = 0.05.
(c) Estimate σ2 for this model.
(d) Compare the estimate of σ2 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.