Pert & Gantt Charts

PERT => Program Evaluation and Review Technique

You can also estimate an activity's duration by using the Program Evaluation and Review Technique (PERT) formula. PERT weighs the average of the pessimistic (P), most likely (M), and optimistic (O) estimates for an activity. For example:

PERT formula = (P+4M+O) / 6

In the following example there are seven tasks, labeled a through g. Some tasks can be done concurrently (a & b) while others cannot be done until their predecessor task is complete (c cannot begin until a is complete). Additionally, each task has three time estimates: the optimistic time estimate (a), the most likely or normal time estimate (m), and the pessimistic time estimate (b). The expected time (TE) is computed using the formula (a + 4m + b) /6.

A Gantt chart is a popular type of bar chart that illustrates a project schedule. Gantt charts illustrate the start and finish dates of the terminal elements and summary elements of a project. Terminal elements and summary elements comprise the work breakdown structure of the project. Some Gantt charts also show the dependency (i.e., precedence network) relationships between activities.

Gantt charts don't illustrate task dependencies & PERT charts can be confusing, PMs often use both.

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