Page 169 - DEDU503_EDUCATIONAL_MANAGEMENT_ENGLISH

Unit 13: Concept of PERT and CPM

13.9 Steps in CPM Project Planning Notes

1. Specify the individual activities.
2. Determine the sequence of those activities.
3. Draw a network diagram.
4. Estimate the completion time for each activity.
5. Identify the critical path (longest path through the network)
6. Update the CPM diagram as the project progresses.
1. Specify the Individual Activities
From the work breakdown structure, a listing can be ma1de of all the activities in the project.
This listing can be used as the basis for adding sequence and duration information in later
steps.
2. Determine the Sequence of the Activities
Some activities are dependent on the completion of others. A listing of the immediate
predecessors of each activity is useful for constructing the CPM network diagram.
3. Draw the Network Diagram
Once the activities and their sequencing have been defined, the CPM diagram can be drawn.
CPM originally was developed as an activity on node (AON) network, but some project planners
prefer to specify the activities on the arcs.
4. Estimate Activity Completion Time
The time required to complete each activity can be estimated using past experience or the
estimates of knowledgeable persons. CPM is a deterministic model that does not take into
account variation in the completion time, so only one number is used for an activity’s time
estimate.
5. Identify the Critical Path
The critical path is the longest-duration path through the network. The significance of the
critical path is that the activities that lie on it cannot be delayed without delaying the project.
Because of its impact on the entire project, critical path analysis is an important aspect of project
planning.
The critical path can be identified by determining the following four parameters for each activity
:
• ES – earliest start time : the earliest time at which the activity can start given that its
precedent activities must be completed first.
• EF – earliest finish time, equal to the earliest start time for the activity plus the time
required to complete the activity.

• LF – latest finish time : the latest time at which the activity can be completed without
delaying the project.
• LS – latest start time, equal to the latest finish time minus the time required to complete
the activity.
The slack time for an activity is the time between its earliest and latest start time, or between its
earliest and latest finish time. Slack is the amount of time that an activity can be delayed past
its earliest start or earliest finish without delaying the project.
The critical path is the path through the project network in which none of the activities have
slack, that is, the path for which ES = LS and EF = LF for all activities in the path. A delay in the

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