1. For  the  situation and  data  described in Exer- cise 17.17, perform conventional multiple regression and stepwise regression analyses on the data, then compare the results of the two approaches. Use total operating revenue as the dependent variable and number of aircraft, number of employees, and number of aircraft departures as the three independent variables. The data are  in  file XR17017.

2. An officer training program has 9 board members who provide ratings for the candidates. The high and low scores are dropped before the overall rating is computed.

For a sample of 28 persons from the most recent class  of candidates, the overall ratings and ratings by the indi- vidual board members are provided in data file XR17055.

a. Construct the correlation matrix for all 10 variables.

b. With overall rating as the dependent variable, per- form a stepwise regression and interpret the results.

c. From the results in part (b), does it appear that the size of the board could be reduced without losing very much explanatory power? Explain.

d. Using only the data provided by the first two board members introduced in part (b), perform a multiple regression analysis. Compare the results with the step- wise regression as it appeared following the introduc- tion of these board members.