Refer to the data in Table 12-13 on order fulfillment time.

(a) You believe that there are differences, in general, in the value of orders by location of the store. Consequently, its impact on order fulfillment time may be influenced as such. Find the model equation based on order value, number of products, store location, and interaction between order value and location. Is the model significant at α = 0.05? What hypotheses are tested in this case?

(b) Are all the predictors significant in the presence of others? Use α= 0.05.

(c) Based on the tests in part (b), what terms would you recommend for inclusion in the model?