a technique for planning, estimating and scheduling projects which was developed in 1958 by the U.S. Navy Special Projects Office, Bureau of Ordnance, in cooperation with Booz, Allen and Hamilton, a management consulting firm. PERT was originally used to develop the Navy's Polaris Weapon System. It utilizes the definition of a methodology for the completion of a project. A PERT network depicts the precedent relationships that exists between various phases, activities or operations, so that critical activities can be identified and the appropriate scheduling and resource allocations can be made. PERT was originally derived from the Critical Path Method (CPM). Like CPM, PERT also expresses nodes in the network and tries to express critical activities in the development of a project. The difference between PERT and CPM is basically that CPM uses one estimate and schedule, while CPM uses three: minimum, maximum and probable. (See Critical Path Method).