7.2. Collecting the Data

Each sales representative works his or her own territory, which is a geographic region of the United Kingdom defined by a collection of postal codes. A given territory contains physicians arranged in practices, where each physician has a particular medical specialty. The physicians write prescriptions for patients who visit their practices, aiming to provide them with the best possible care within the prevailing constraints. A sales representative will periodically make calls on a prescribing physician to promote the use of Pharma Inc.'s products, while representatives from competing companies do the same thing. During a visit, if a promotion is running, the sales representative may leave behind a promotional sample kit. Sales representatives control their own time and, before Rick joined, typically met with their sales manager about once a year.

Rick downloads company data on the performance of the sales representatives for May through December 2008 into a Microsoft® Excel spreadsheet. He intends to use this data to address both of the questions posed by his manager. He realizes that there has been some turnover in the sales force in 2008, but this has been minor. For his purposes, Rick decides that he will only include data for sales representatives who dealt with the same physicians for the entire eight-month period. He eliminates those few sales representatives who were active for only a portion of the eight months.

At this point, Rick easily imports ...

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