premise: Part of the reason for the difference in pieces per possible delivery may be due to the fact that five percent of possible residential deliveries are businesses , and it is thought , but not known , that a lesser percentage of possible deliveries on rural routes are businesses .
hypothesis: It is thought , but not known , that a lesser eprcentage of possible deliveries on rural routes are businesses , and part of the reason for the difference in pieces per possible delivery , may be due to the fact that five percent of possible residential deliveries are businesses .