PERT Definition In Project Management:
PERT Network (Program Evaluation and Review Technique) is used to assist in project scheduling similar to CPM. However, it assumes that activity durations are random variables (i.e., probabilistic).
Two related operations research techniques, PERT (program evaluation and review technique) & CPM (critical path method), are available to assist the construction manager or project manager in carrying out these responsibilities. These techniques make heavy use of networks to help plan & display the coordination of all the activities. They normally use a software package to deal with all the data needed to develop a time schedule information and then to control and monitor the progress of the project.
PERT definitions for the time required to accomplish an activity:
- Optimistic Time, which is the least amount of time to finish an activity or task.
- Pessimistic Time, which is the maximum amount of time to finish an activity or task.
- Most Likely Time, which is the best estimate of how long it will take to finish the activity or task, assuming there are no problems.
- Expected Time, which is the best estimate of how long it will take to finish the activity or task, assuming there will be problems.
How To Calculate duration using PERT Technique
shortest time + (4 x likely time) + longest time
Steps to Implementing a PERT Network
- Determine the activities required to complete the project, the order in which they must be done & their duration.
- Create a network diagram with arrows (AOA) representing activities & nodes being milestones.
- What are the critical path & possible float?
Difference Between CPM And PERT
1. Critical Path Method is activity oriented whereas PERT is event oriented. In simple words, in PERT network is focused upon start or finish of events and not on activities themselves.
2. In CPM network no allowance is made for uncertainties in the duration of time involved whereas uncertainty is considered in PERT.
3. In PERT, time isn’t related to cost whereas in CPM the object is to develop an optimum time cost relationship. However, PERT has since been extended in this direction and the line dividing CPM/PERT is gradually fading out.
4. In PERT duration of activities aren’t so accurate and definite whereas in CPM duration of activity is estimated with a fair degree of accuracy.
5. In Critical Path Method, both cost and time can be controlled during planning. Pert is basically a tool for planning.
6. CPM is widely used in construction projects whereas the Program Evaluation and Review Technique is used in a research and development project, basically for non-repetitive type projects.