Use the computer output for the Business Week magazine data of Problem 13 in Chapter 8, as well as the additional output here, to answer the following questions.
a. Perform the overall F test for the regression of Y on both independent variables, X2 and X1. Interpret your result.
b. Perform variables-added-in-order tests for both independent variables, with X2 added first.
c. Perform variables-added-in-order tests for both independent variables, with X3 added first.
d. Provide a table of variables-added-last tests.
e. Which predictors appear to be necessary? Why?