Page 242 - DMGT521_PROJECT_MANAGEMENT

Unit 13: PERT, CPM and Time Estimation

13.12 Summary Notes

 CPM was the discovery of M.R. Walker of E.I. DuPont de Nemours & Co. and J.E. Kelly of
Remington Rand, circa 1957.

 PERT was devised in 1958 for the POLARIS missile program by the Program Evaluation
Branch of the Special Projects office of the U.S. Navy.

 There have been several extensions to both network and chart forms of project scheduling.
 Planning, Scheduling (or organising) and Control are considered to be basic Managerial
functions.

 In our Social Project, the Project Manager is now not so certain that each activity will be
completed on the basis of the single estimate.
 The Beta distribution is appropriate for calculation of activity durations.

 One shortcoming of the PERT/CPM network method is that it does not allow for leads and
lags between two activities without greatly increasing the number of sub-activities to
account for this.
 Far more than the technical benefits, it was found that PERT/CPM provided a focus around
which managers could brainstorm and put their ideas together.

 There are many variations of PERT/CPM which have been useful in planning costs,
scheduling manpower and machine time.

13.13 Keywords

Critical Path: Critical Path is the longest pathway taken from the initial event to the terminal
event.
Expected Length of a Project: It is simply the sum of their separate expected lengths.
Free Float: It is the spare time available when all preceding activities occur at the earliest possible
times and all succeeding activities occur at the earliest possible times.
Pessimistic Time: Pessimistic time (P) is the maximum possible time required to accomplish a
task, assuming everything goes wrong (but excluding major catastrophes).

PERT: PERT assumes that the expected length of a project (or a sequence of independent activities)
is simply the sum of their separate expected lengths.
Slack: The slack of an event is a measure of the excess time and resources available in achieving
this event. Positive slack would indicate ahead of schedule; negative slack would indicate behind
schedule; and zero slack would indicate on schedule.
Time Estimation: Accurate time estimation is a skill essential for good project management.
Total Float: It is the spare time available when all preceding activities occur at the earliest
possible times and all succeeding activities occur at the latest possible times.
13.14 Review Questions

1. Describe about the brief history and language of CRM.
2. Discuss about the framework of PERT and CPM.
3. Discuss about Network Techniques of Project Management.

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