Refer to Grocery retailer Problem 6.9. The observations are listed in time order. Assume that regression model (12.2) is appropriate. Test whether or not positive autocorrelation is present; use α = .05. State the alternatives, decision rule, and conclusion
Problem 6.9
Grocery retailer. A large, national grocery retailer tracks productivity and costs of its facilities closely. Data below were obtained from a single distribution center for a one-year period. Each data point for each variable represents one week of activity. The variables included are the number of cases shipped (XI)' the indirect costs of the total labor hours as a percentage (X2), a qualitative predictor called holiday that is coded 1 if the week has a holiday and 0 otherwise (X3), and the total labor hours (Y).
a. Prepare separate stem-and-leaf plots for the number of cases shipped Xit and the indirect cost of the total hours Xi2. Are there any outlying cases present? Are there any gaps in the data?
b. The cases are given in consecutive weeks. Prepare a time plot for each predictor variable. - What do the plots show?
c. Obtain the scatter plot matrix and the correlation matrix. What information do these diagnostic aids provide here?