Consider the rocket propellant data in Exercise 11-12.
(a) Calculate R2 for this model. Provide an interpretation of this quantity.
(b) Plot the residuals on a normal probability scale. Do any points seem unusual on this plot?
(c) Delete the two points identified in part (b) from the sample and fit the simple linear regression model to the remaining 18 points. Calculate the value of R2 for the new model. Is it larger or smaller than the value of R2 computed in part (a)? Why?
(d) Did the value of change dramatically when the two points identified above were deleted and the model fit to the remaining points? Why?