The manager of the Valley Forge post office is interested in the amount of time that window clerks spend on ancillary services such as selling special issue stamp sets or commemorative T-shirts and helping customers with passport applications. Three clerks, each earning $36,000 per year, staff the windows. When they are not needed at the window, they sort mail for the carriers. The results of a preliminary work sampling study are shown in Table H.7, where entries reflect number of occurrences.
a. For a degree of precision of ±0.05, what is the sample size adequate for special stamp sets? For T-shirts?
For passports? What proportion of time do the clerks spend on each activity?
b. If a machine to sell special stamps could be purchased outright for $3,500, would you recommend buying it? Discuss.

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TABLE H.7 VALLEY FORGE WORK SAMPLING DATA Selling Postage Day Priority Mail Special Stamp Sales T-Shirt Sales Other Total Passports 1 1 2 10 1 1 10 1 10 4 1 1 10 8 1 10 6 10 1 1 1 10 1 10 8 10 6. 1 10 10