The data elements used in this study  the number of addresses served; the number of stops; (for city carriers only) volume per address, and address per kilometer (for rural carriers only).
Volume per address was only studied for rural carriers only.
mnli hypothesis: Volume per address was only studied for rural carriers only. premise: The data elements used in this study  the number of addresses served; the number of stops; (for city carriers only) volume per address, and address per kilometer (for rural carriers only).