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The per-store daily customer count (i.e., the mean number

of customers in a store in one day) for a nationwide convenience

store chain that operates nearly 10,000 stores has been

steady, at 900, for some time. To increase the customer count,

the chain is considering cutting prices for coffee beverages. The

question to be determined is how much to cut prices to increase

the daily customer count without reducing the gross margin on

ISBN 1-269-14496-0

Business Statistics: A First Course, Sixth Edition, by David M. Levine, Timothy C. Krehbiel, and Mark L. Berenson. Published by Prentice Hall.

Copyright © 2013 by Pearson Education, Inc.

Problems for Section 10.5 379

coffee sales too much. You decide to carry out an experiment in

a sample of 24 stores where customer counts have been running

almost exactly at the national average of 900. In 6 of the

stores, the price of a small coffee will now be $0.59, in 6 stores

the price of a small coffee will now be $0.69, in 6 stores, the

price of a small coffee will now be $0.79, and in 6 stores, the

price of a small coffee will now be $0.89. After four weeks of

selling the coffee at the new price, the daily customer count in

the stores was recorded and stored in .

a. At the 0.05 level of significance, is there evidence of a

difference in the daily customer count based on the price

of a small coffee?

b. If appropriate, determine which prices differ in daily customer

counts.

c. At the 0.05 level of significance, is there evidence of a

difference in the variation in daily customer count among

the different prices?

d. What effect does your result in (c) have on the validity of

the results in (a) and (b)?

10.62 Integrated circuits are manufactured on silicon wafers

through a process that involves a series of steps. An experiment

was carried out to study the effect on the yield of using three

methods in the cleansing step (coded to maintain confidentiality).

The results (stored in Yield-OneWay ) are as follows:

CoffeeSales