For the data given in Problem 11 in Chapter 7, which concerns the relationship between the temperature (X) of a certain medium and the growth (Y) of human amniotic cells in a tissue culture, researchers wish to evaluate whether a parabolic model is more appropriate than a straight-line model. Use the accompanying computer output to answer the following questions:
a. Plot the fitted straight-line model and the fitted quadratic model on the same scatter diagram.
b. Test for the significance of adding the X2 term to the model.
c. Determine the change in R2 in going from a straight-line to a parabolic model.
d. How do your results in parts (b) and (c) compare with the results in Problem 11 in Chapter 7 for the test of adequacy of fit of the straight-line model?
e. Which model is more appropriate—straight line or parabolic?