Explain the differences between a Gantt chart and a PERT/CPM chart.

What will be an ideal response?

A Gantt chart is a horizontal bar chart that represents a schedule. In a Gantt chart, time is displayed on the horizontal axis and the activities are arranged vertically, from top to bottom, in the order of their start dates. The chart contains a horizontal bar for each task or group of tasks. The horizontal position of each bar shows the start and end of the activity, and the length of the bar indicates its duration.
A Gantt chart can be used to report the status of a project by showing a comparison of scheduled progress for a task against actual progress for that task. Using various graphic techniques, as shown in Figure 3-4, a Gantt chart can show the amount of work completed versus the amount of work not yet finished. Although Gantt charts present a clear picture of project status, they are not an ideal tool for project control because they do not show task dependencies. Therefore, you cannot determine the impact on the entire project caused by a single task that falls behind schedule. Also, a Gantt chart shows the time span, but not the specific number of hours or person-days, required.
A PERT/CPM chart shows a project as a network diagram. Traditionally, the activities are shown as vectors, or lines, and the events are displayed as circular or rectangular nodes. Vectors on a PERT/CPM chart show task dependencies, but they do not indicate the duration of the activities they represent. Instead, the estimated duration of the activity appears below the vector. PERT/CPM charts also use a dashed vector line to represent a dummy activity, which indicates an event dependency, but does not require any resources or completion time.
One advantage of PERT/CPM charts is that, unlike Gantt charts, all tasks and dependencies are shown, and PERT/CPM charts can be used for scheduling, monitoring, and controlling projects. PERT/CPM charts can be rather complicated, however, especially for larger projects. Also, the overall picture presented by a PERT/CPM chart is not as clear as a Gantt chart, which graphically displays the timing and duration of the activities.