Program Evaluation and Review Technique (Pert)

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Program Evaluation and Review Technique (PERT) is a scheduling method originally designed to plan a manufacturing project by employing a network of interrelated activities, coordinating optimum cost and time criteria. PERT emphasizes the relationship between the time each activity takes, the costs associated with each phase, and the resulting time and cost for the anticipated completion of the entire project. PERT is an integrated project management system. These systems were designed to manage the complexities of major manufacturing projects, the extensive data necessary for such industrial efforts, and the time deadlines created by defense industry projects. Most of these management systems developed following World War II, and each has its advantages. PERT was first developed in 1958 by the U.S. Navy Special Projects Office on the Polaris missile system. Existing integrated planning on such a large scale was deemed inadequate, so the Navy pulled in the Lockheed Aircraft Corporation and the management consulting firm of Booz, Allen, and Hamilton. Traditional techniques such as line of balance, Gantt charts, and other systems were eliminated, and PERT evolved as a means to deal with the varied time periods it takes to finish the critical activities of an overall project. The line of balance (LOB) management control technique collected, measured, and analyzed data to show the progress, status, and timing of production projects. It was introduced at Goodyear Tire and Rubber Company in 1941 and fully utilized during World War II in the defense industry. Even older is the Gantt chart, developed during World War I by Harvey Gantt, a pioneer in the field of scientific management. It is a visual management system, on which future time is plotted horizontally and work to be completed is indicated in a vertical line. The critical path method (CPM) evolved parallel to PERT. CPM is a mathematically ordered network of planning and scheduling project management; it was first used in 1957 by E.I. du Pont de Nemours & Co. PERT borrows some CPM applications. PERT proved to be an ideal technique for one-of-a-kind projects, using a time network analysis to manage personnel, material resources, and financial requirements. The growth of PERT paralleled the rapid expansion in the defense industry and meteoric developments in the space race. After 1960, all defense contractors adopted PERT to manage the massive one-time projects associated with the industry. Smaller businesses, awarded defense related government contracts, found it necessary to use PERT. At the same time, du Pont developed CPM, which was particularly applied in the construction industry. In the last 30 years, PERT has spread, as has CPM, as a major technique of integrated project management. PERT centers on the concept of time and allows flexible scheduling due to variations in the amount of time it takes to complete one specific part of the project. A typical PERT network consists of activities and events. An event is the completion of one program component at a particular time. An activity is defined as the time and resources required to move from one event to another. Therefore, when events and activities are clearly defined, progress of a program is easily monitored, and the path of the project proceeds toward termination. PERT mandates that each preceding event be completed before succeeding events, and thus the final project, can be considered complete. One key element to PERT's application is that three estimates are required because of the element of uncertainty and to provide time frames for the PERT network. These three estimates are classed as optimistic, most likely, and pessimistic, and are made for each activity of the overall project. Generally, the optimistic time estimate is the minimum time the activity will take—considering that all goes right the first time and luck holds for the project. The reverse is the...
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