Refer to Grocery retailer Problem 6.9.
a. Transform the variables by means of the correlation transformation (7.44) and fit the standardized regression model (7.45).
b. Calculate the coefficients of determination between all pairs of predictor variables. Is it meaningful here to consider the standardized regression coefficients to reflect the effect of one predictor variable when the others are held constant?
c. Transform the estimated standardized regression coefficients by means of (7.53) back to the ones for the fitted regression model in the original variables. Verify that they are the same as the ones obtained in Problem 6. lOa.
Problem:
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?