# RF Wireless World

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## PERT chart vs GANTT chart-Difference between PERT chart and GANTT chart

This page compares PERT chart vs GANTT chart and mentions difference between PERT chart and GANTT chart. The other difference between terms are also covered.

### PERT chart

"Program Evaluation and Review Technique" is the full form of term PERT. PERT chart is basically a network diagram. In Critical Path Method(CPM) the activity durations are based on historic data which has been performed many times. Think of a situation wherein activity is not performed earlier and it has been performed first time in the organization. This is the time PERT is useful. Hence difference between CPM and PERT is that:
• CPM is used when the timelines of the activities are deterministic
• PERT is used when timelines are not deterministic

Fig.1

PERT uses three time estimates to come to a conclusion regarding time estimates for a activity.
➨Optimistic Time(O): It is the shortest time in which the activity can be completed.
➨Pessimistic Time(P):It is the longest time an activity might be needed.
➨Most likely Time(M):It is the completion time which has the highest probability.

Figure mentions three equations to calculate activity time duration, standard deviation and standard variance.

### GANTT chart

It is the time and activity bar chart. Gantt charts are simple chart which display project schedule in task sequence and by the task start and finish dates.

Fig.2

Figure-2 depicts simple activity network diagram mentioning activity and time duration in weeks. As mentioned Activity-A requires 1 week, B requires 2 weeks, C requires 2 weeks, D requires 1 week and E requires 1 week.

Simple Gantt chart for the above activities is mentioned below in figure-3. As mentioned Gantt chart is the illustration of the time and activities.

As mentioned activities is listed on the vertical axis and time scale is listed on the horizontal exis. As shown activity bar represents the duration of all the activities representing all the tasks from A to E.

Gantt chart does not show clear dependencies or relationships between tasks for example, which task comes first, then second and so on. It also fails in showing the critical and non critical tasks. Gantt chart is best used to show summary of the whole project to the top management as it does not show detail information for every activity.

Fig.3