1. INTRODUCTION
A big establishment project like construction of highway, design development, and marketing of new product can be split into small tasks with sequence od their execution. The time required to complete each task can be estimated and must be finished by that time. The main objectives of doing so are to plan and manage the resources required to complete the project, to finish the work within the specified time. In most planning, network analysis is used, and PERT and CPM are the two methods to analyze the network, discussed in the following headings.
2. PERT(PROGRAMME EVALUATION AND REVIEW TECHNIQUE)
PERT was developed in the time of 1950s where the completion time of the project had to be based upon probability, which is a requirement of three-time estimates,i.e., optimistic time, pessimistic time, and the most likely time. They are then mathematically analyzed to determine the probable time of the completion. It is best suited for R&D work where certain uncertainties exist. They consist of events required to achieve the project objectives, and all the operations are non-repetitive.
3. CPM(CRITICAL PATH METHOD)
It is a methodology used to assist in the building and maintenance of a chemical plant.CPM is used where the project has certainties for the completion of time. The whole project consists of some operations called activities. They are generally referred to as activity-oriented diagrams in which arrows represent the activities, and the sequence of arrows indicates the sequence. They are repetitive in nature and are very useful for construction projects.
4. TERMINOLOGY USED IN PERT AND CPM
- Event-Start or completion of an activity occurring at any instant time at which some part of the project has been completed is called an event. They are of the following types:
- Successor events-The events which follow other events are called successor events.
- Predecessor events-The events which occur before another event is called a predecessor event to that event.
- Activity-It represents the distinct operation to be done as the project proceeds. An activity can be predecessor activity, successor activity, and dummy activity. They have a major role in CPM.
- Dummy Activity-Any activity that does not consume any resource or time is called a dummy activity. These are nonreal activities and are used to preserve the logic of the network and used when two activities have the same predecessor activities.
5. SIMILARITIES AND DIFFERENCES BETWEEN PERT AND CPM
5.1 SIMILARITIES
- Both methodologies are used for project planning and scheduling by developing and analyzing the network diagram andand splitting the project into smaller tasks.
- The rules for drawing the network for both are the same.
- The critical path is found in both cases.
5.2 DIFFERENCES
- CPM is activity-oriented and is based on the analysis of the progress of activities.PERT is event-oriented and is based on the progress of events.
- PERT uses three-time estimates, and an expected completion time is required by probabilistic approach, whereas CPM provides normal time for project completion
- PERT is used for Research and Development programs, whereas CPM is used for construction projects.
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