The Project Evaluation Review Technique, or PERT, is used in project management to determine the time required to complete a specific task or activity.
What is Project Evaluation Review Technique (PERT)?
It is a system that aids in the proper scheduling and coordination of all project tasks. It also helps in keeping track of the overall project’s progress, or lack thereof. The US Navy developed the Project Evaluation Review Technique in the 1950s to manage the Polaris submarine missile program of their Special Projects Office.
Knowing how long it should take to complete a project is crucial because it helps project managers decide on other factors such as budget and task delegation. Estimates can be overly optimistic or pessimistic, regardless of how large or small a project is, but using a PERT chart will help determine realistic estimates.
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
PERT formula:
shortest time + (4 x likely time) + longest time
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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 and 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 the start or finish of events and not on activities themselves.
2. In the 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 the 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.
Advantages of PERT in Project Management
- Improved planning &scheduling of activities.
- Improved forecasting of resource requirements.
- Identification of repetitive planning patterns that can be followed in other projects, then simplifying the planning process.
- Ability to see and then reschedule activities to reflect interproject dependencies & resource limitations following know priority rules.
- It also provides the following: expected project completion time, probability of completion before a specified date, the critical path activities that impact completion time, the activities that have slack time, and that can lend resources to critical path activities, and activity start and finish dates.
Disadvantages of PERT
- Many people find PERT difficult to grasp in complex projects, thus they may instead use a Gantt Chart, another popular project management method.
- It can be tedious to update, modify, and maintain the PERT diagram.
- It requires a subjective time analysis of activities, which may have an impact on the project’s schedule for people who are less experienced or biased.
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