Refer to Grocery retailer Problem 6.9. Assume that regression model (6.5) for three p1-edictor variables with independent normal error terms is appropriate.
a. Management desires simultaneous interval estimates of the total labor hours for the following five typical weekly shipments:
Obtain the family of estimates using a 95 percent family confidence coefficient. Employ the Working-Hotelling or' the Bonfemmi procedure, whichever is more efficient.
b. FOI' the data in Problem 6.9 on which the regression fit is based, would you consider a shipment of 400,000 cases with an indirect percentage of 7.20 on a nonholiday week to be within the scope of the model? What about a shipment of 400,000 cases with an indirect percentage of9.9 on a nonholiday week? Support your answers by preparing a relevant plot.
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?