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Q.1 Explain Relationship between PERT & CPM. Also describe the framework required for PERT & CPM

PERT and CPM are the project management techniques created for the need of the Western and Military Establishments to plan, schedule and control the complex projects. CPM/PERT developed along two parallel streams – one industrial and the other military.

CPM was first introduced by M. R. Walker and J. E. Kelly. This computation was designed for the UNIVAC-I computer. The first test was made in 1958, when CPM was applied in the construction of a new chemical plant. In March 1959, the CPM was applied in the planned shutdown at the Du Pont works in Louisville, Kentucky. The introduction of CPM greatly reduced the unproductive time from the 125 hours to the 93 hours.

PERT was introduced first for the POLARIS missile program by the Program Evaluation Branch of the Special Projects office of the U.S. Navy. The calculations were so arranged so that they could be performed in the IBM Naval Ordinance Research Computer (NORC) at Dahlgren, Virginia. Rather than giving technical benefits, it is found that PERT/CPM provides a focus around which managers could brain-storm and can put their ideas.

PERT/CPM is a great communication medium by which thinkers and planners at one level can communicate their ideas, their doubts and fears for another level. Another important feature of the PERT/CPM is that it is a useful tool for evaluating the performance of the individuals and the teams.
There are many variations of CPM/PERT which have been useful in planning costs, scheduling manpower and machine time. CPM/PERT can answer following important questions –How long will the entire project take to be completed? What are the risks involved in this?
Which are the critical activities or tasks in the project which could delay the entire project if they were not completed on time?
Is the project on schedule, behind schedule or ahead of schedule?
If the project has to be finished earlier than the planned, what is the best way to do this at the least cost?

The Framework for PERT and CPM
There are six steps which are common to both the techniques. The procedure is as follows –
1. Define the Project and all of its significant activities or tasks. The project (made up of several tasks) should have only a single start activity and a single finish activity.
2. Develop the relationships among the activities. Decide which activities must precede and which must follow others.
3. Draw the ‘Network’ connecting all the activities. Each activity should have unique event numbers. Dummy arrows are used where required to avoid giving the same numbering to two activities.
4. Assign time and/or estimates to each activity.
5. Compute the longest time path through the network. This is called the critical path.
6. Use the network to help plan, schedule, monitor and control the project.
The key concept used by both in PERT as well as CPM is that a small set of activities, which make up the longest path through the activity network control the entire project. If these ‘critical’ activities could be identified and assigned to the responsible persons, management resources could be optimally used by concentrating on the few activities which determine the fate of the entire project.

The non-critical activities can be re-planned, rescheduled and resources for them can be reallocated flexibly, without affecting the whole project. The five important questions that should be asked before the preparation of an activity network are the following –
•Is this a Start Activity?
•Is this a Finish Activity?
•What activity precedes this?
•What activity follows this?
•What activity is concurrent with this?

Some activities are serially linked. The second activity can begin only after the first activity is completed. In the certain cases, the activities are concurrent, because they are independent of each other and can start simultaneously. This is essentially the case in organizations which have supervisory resources so that work can be delegated to various departments that will be responsible for the activities to be performed and their completion as per the planning.


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