Page 173 - DCAP304_DCAP515_SOFTWARE_PROJECT_MANAGEMENT

Unit 9: CPM /PERT

There are many variations of CPM/PERT which have been useful in planning costs, scheduling Notes
manpower and machine time. CPM/PERT can answer the following important questions:
 How long will the entire project take to be completed? What are the risks involved?

 Which are the critical activities or tasks in the project which could delay the entire project
if they were not completed on time?
 Is the project on schedule, behind schedule or ahead of schedule?
 If the project has to be finished earlier than planned, what is the best way to do this at the
least cost?

9.1.1 Framework for PERT and CPM

Essentially, there are six steps which are common to both the techniques. The procedure is listed
below:
1. Define the Project and all of it’s significant activities or tasks. The Project (made up of
several tasks) should have only a single start activity and a single finish activity.
2. Develop the relationships among the activities. Decide which activities must precede and
which must follow others.

3. Draw the “Network” connecting all the activities. Each Activity should have unique event
numbers. Dummy arrows are used where required to avoid giving the same numbering
to two activities.

4. Assign time and/or cost estimates to each activity
5. Compute the longest time path through the network. This is called the critical path.
6. Use the Network to help plan, schedule, monitor and control the project.
The Key Concept used by CPM/PERT is that a small set of activities, which make up the longest
path through the activity network control the entire project.

Notes If these “critical” activities could be identified and assigned to responsible persons,
management resources could be optimally used by concentrating on the few activities
which determine the fate of the entire project.
Non-critical activities can be replanned, rescheduled and resources for them can be reallocated
flexibly, without affecting the whole project.

Five useful questions to ask when preparing an activity network are:
 Is this a Start Activity?
 Is this a Finish Activity?
 What Activity Precedes this?

 What Activity Follows this?
 What Activity is Concurrent with this?
Some activities are serially linked. The second activity can begin only after the first activity is
completed. In certain cases, the activities are concurrent, because they are independent of each
other and can start simultaneously. This is especially the case in organizations which have
supervisory resources so that work can be delegated to various departments which will be
responsible for the activities and their completion as planned.

LOVELY PROFESSIONAL UNIVERSITY 167