useful management tool for planning, coordinating, and controlling large, complex projects such as formulation of a master (COMPREHENSIVE) budget, construction of buildings, installation of computers, and scheduling of the closing of books. The development and initial application of PERT dates to the construction of the Polaris submarine by the U.S. Navy in the late 1950s. The PERT technique involves the diagrammatical representation of the sequence of activities comprising a project by means of a network consisting of arrows and circles (nodes), as shown in Figure 1. Arrows represent tasks" or "activities," which are distinct segments of the project requiring time and resources. Nodes (circles) symbolize "events," or milestone points in the project representing the completion of one or more activities and/or the initiation of one or more subsequent activities. An event is a point in time and does not consume any time in itself as does an activity. An important aspect of PERT is the Critical Path Method (CPM). A path is a sequence of connected activities. In Figure 1, 2-3-4-6 is an example of a path. The critical path for a project is the path that takes the greatest amount of time. This is the minimum amount of time needed for the completion of the project. Thus, activities along this path must be shortened in order to speed up the project. To compute this, calculate the time (ET) and the latest time (LT) for each event.
In a real-world application of PERT to a complex project, the estimates of completion time for activities will seldom be certain. To cope with the uncertainty in activity time estimates, proceed with three time estimates: an optimistic time (labeled a), a most likely time (m), and a pessimistic time (b). A weighted average of these three time estimates is then calculated to establish the expected time for the activity. The formula is: ( a + 4m + b )/6. For example, given three time estimates, a = 1, m = 3, and b = 5, the expected time is [1 + 4(3) + 5]/6 = 3.
planning and control technique to minimize interruptions and/or delays in a process with interrelated functions. PERT is used to assist in reducing the time required for completion of a project.
