After several years of decreased sales for advertisements on its bus lines, the Arthursville Transportation System (ATS) reorganized its sales force. Before reorganization, its sales force was stratified, with the more experienced sales representatives targeting the most promising opportunities. The reorganization introduced a relationship-based approach by which sales representatives are assigned based on their social proximity to specific buyers. After the reorganization, revenue from advertising sales increased.
In evaluating whether the increase in advertising sales can reasonably be attributed to the reorganization, it would be most useful to determine which of the following?