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•Adjust variance formula for level of precision (99+, 95, or 90).

Figure 8-19: Template formulas for PERT spreadsheet.

•Adjust variance formula for level of precision (99+, 95, or 90).

Figure 8-19: Template formulas for PERT spreadsheet.

There are several advantages to the use of Gantt charts. First, even though they may contain a great deal of information, they are easily understood. While they do require frequent updating (as does any scheduling/control device), they are easy to maintain as long as task requirements are not changed or major alterations of the schedule are not made. Gantt charts provide a clear picture of the current state of a project.

Another significant advantage of Gantt charts is that they are easy to construct. While they may be constructed without first drawing a PERT diagram, there is a close relationship between the PERT/CPM network and the Gantt chart. We use the example in the previous section to illustrate this relationship and, at the same time, demonstrate how to construct such a chart.

First, the PERT/CPM network of Figure 8-15 is redrawn so that the lengths of each arc are in proportion to the respective task times. In essence, we redraw the network along a horizontal time scale. This modified network is shown in Figure 8-20. The heavy line, a-d-| is the critical path, and the horizontal dashed line segments indicate slack times. The vertical dashed line segments are dummy activities (as between events 3 and 4), or merely connectors (as elsewhere in the drawing). Note that to transform the network in this manner requires that we "explode" single nodes into multiple nodes when multiple activities emanate from the single node. In this modified network, each activity must originate from an individual node, although several activities still can have a common destination node.

The nodes of Figure 8-15 are placed at their EOTs (the early start times for ensuing activities), and the slack is shown after the activity duration. (We have used an arrowhead to separate the activity duration from its slack.) To draw the modified diagram only requires that the nodes be placed at their EOTs listed on the PERT/CPM network and the activity durations drawn out from them as solid lines. Precedence is shown by connecting the duration lines with dashed line segments, showing each specific connection to the appropriate nodes.

The Gantt chart can be drawn directly from the modified PERT/CPM diagram. A list is made of all activities required to complete the project. Activities are usually listed in alphanumeric order—which is most often the order in which they were

Days

Figure 8-20: Gantt chart style representation of PERT/CPM network in Figure 8-15.

Days

Figure 8-20: Gantt chart style representation of PERT/CPM network in Figure 8-15.

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Project Management Made Easy

Project Management Made Easy

What you need to know about… Project Management Made Easy! Project management consists of more than just a large building project and can encompass small projects as well. No matter what the size of your project, you need to have some sort of project management. How you manage your project has everything to do with its outcome.

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