Basic Marketing Research with Excel 3rd Edition by Alvin Burns,Ronald Bush

Exercise 18

Target: Deciding on the Number of Telephone Numbers
Target is a major retail store chain specializing in goodquality merchandise and good values for its customers. Currently, Target operates about 1,700 stores, including over 200 Super Targets, in major metropolitan areas of forty-eight of the U.S. states. One of the core marketing strategies employed by Target is to ensure that the shopper has a special experience every time he or she shops at Target. This special shopping experience is enhanced by Target's department arrangements that are intuitive (e.g., toys are next to sporting goods). Another shopping experience feature is the "racetrack" or extra wide center aisle that helps shoppers navigate the store easily and quickly. A third feature is the aesthetic appearance of its shelves, product displays, and seasonal specials. Naturally, Target continuously monitors the opinions and satisfaction levels of its customers because competitors are constantly trying to outperform Target, and/or customers' preferences change.
Target management has committed to an annual survey of 1,000 of its customers to determine these very issues and to provide for a constant tracking and forecasting system of its customers' opinions. The survey will include customers of Target's competitors such as Wal-Mart, K-Mart, and Sears. In other words, the population under study is all consumers who shop in mass merchandise stores through Target's geographic markets. The marketing research project director has decided on the use of a telephone survey to be
conducted by a national telephone survey data collection company, and he is currently working with Survey Sampling International (SSI) to purchase the telephone numbers of consumers residing in Target's metropolitan target markets. The SSI personnel have informed him of the basic formula they use to determine the number of telephone numbers needed.
The formula is as follows:
Telephone numbers needed = Completed interviews/(Working phone rate × Incidence × Completion rate)
Where:
Working phone rate _ percent of telephone numbers that are "live"
Incidence = percentage of those reached that will take part in the survey
Completion rate = percentage of those willing to take part in the survey that actually complete the survey
As a matter of convenience, Target identifies four different regions that are roughly equal in sales volume: North, South, East, and West.

With a desired final sample size of 250 for each region, what is the lowest total number of telephone numbers that should be purchased for each region?