Data on sales revenue Y, television advertising expenditures X1, and print media advertising expenditures X2 for a large retailer for the period 1988-1993 were given in Problem 11 of Chapter 8. Use the computer output for that problem, along with the additional portions of the output shown here, to answer the following questions.
a. Perform the overall F test for the regression of Y on both independent variables. Interpret your result.
b. Perform variables-added-in-order tests for both independent variables, with X1 added first.
c. Perform variables-added-in-order tests for both independent variables, with X2 added first.
d. Provide a table of variables-added-last tests.
e. Which predictors appear to be necessary? Why?

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Y Regressed on X1 and X2 Type I SS 28.07164068 Mean Square FVal ue Pr> F Source DF X1 X2 28.07164068 117.82 0.0017 0.04689121 0.04689121 0.20 0.6874 Mean Square F Val SourceDFType IlI SS x1 X2 ue Pr> F 25.89125916 25.89125916 108.66 0.0019 0.20 0.6874 0691212020 0.874