PERT chart definition
/What is a PERT Chart?
A PERT chart gives a visual representation of the critical path of a project. This critical path is the sequence of interdependent activities that will require the longest time period to complete. Each task on the chart is labeled with high and low estimated start and finish times, which can be used to determine where there is slack in the system and where to focus attention on compressing the schedule.
PERT allows for the inclusion of variable amounts of time for each task. Thus, each task has a most likely, pessimistic, and optimistic duration attached to it. The optimistic and pessimistic durations should have a probability in the 10-20% range. These three estimates are then combined to arrive at a single estimated duration for each task. The calculation of this expected task time is as follows:
[(Optimistic estimate) + (4 x Most likely estimate) + (Pessimistic estimate)] ÷ 6
In addition, the chart contains all tasks that must be addressed before a project can be completed, the sequence in which they must be completed, and the time requirements for each one. A PERT chart is especially useful for the management of more complex projects that would overwhelm a Gantt chart.
The PERT acronym is an abbreviation of the term Program Evaluation and Review Technique.
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Advantages of PERT Charts
A key advantage of a PERT chart is that managers can use it to monitor the resources required to complete a project, as well as to estimate how much more time is required to complete it. Another advantage is that a PERT chart identifies exactly who is responsible for each activity in a process, so it is easy to pinpoint who needs to complete which tasks. A further advantage is that a PERT chart can be used to model a variety of different scenarios, to see how variations in the amount of resources applied will alter the outcome of a project.
Disadvantages of PERT Charts
Though PERT charts are generally useful, a potential failing is that projected activity durations are subjective, so the outcomes stated in a chart may not accurately reflect the actual outcome. Another issue is that a significant amount of specialized labor is needed to monitor project activities and applied resources, and update this information within the charting software. In short, PERT chart maintenance is labor-intensive.