Exercise 11-6 presents data on y = steam usage and x = average monthly temperature. (a) What proportion of total variability is accounted for by the simple linear regression model? (b) Prepare a...

Exercise 11-6 presents data on y = steam usage and x = average monthly temperature.
(a) What proportion of total variability is accounted for by the simple linear regression model?
(b) Prepare a normal probability plot of the residuals and interpret this graph.
(c) Plot residuals versus and x. Do the regression assumptions appear to be satisfied?