2. Program Evaluation and Review Technique  (PERT)

PERT was initially used by defiance  in their Polaris project .In this method, the
activities time duration is found using  these following formula:

Duration       = 

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Standard Devation    =       

A network analysis method is used to approximate
project time duration when there is a unpredictability
about the individual activity time duration approximates. PERT applies the
critical path method (CPM) to a weighted average time duration approximate.
This approach was developed about the same time as CPM, in the late 1950s, and
also uses network diagrams concept, which are still sometimes referred to as PERT
charts. PERT uses probabilistic time approximates duration. Approximation based
on using optimistic time, most likely time , and pessimistic time  approximates of activity durations instead of
one specific or discrete duration approximate, as CPM does .By using the PERT
weighted average for each activity duration approximate, the total project
duration approximate takes into account the risk or uncertainty in the
individual activity estimate.


For example:

Suppose A project team in the project case
used PERT to determine the schedule for the online application registration
system project. They would have to collect data for the optimistic, most
likely, and pessimistic duration approximates for each project activity.
Suppose one of the activities was to design an input screen for the system.
Someone might approximate that it would take about two weeks or 10 workdays to
do this activity. Without using PERT, the duration approximate for that
activity would be 10 workdays. Using PERT, the project team would also need to approximate
the pessimistic and optimistic times for completing this activity. Suppose an
optimistic approximate is that the input screen can be designed in eight
workdays, and a pessimistic time approximate is 24 workdays.

Applying the PERT formula:

PERT weighted average = 


                                         = 12

Instead of using the most likely duration approximate
of 10 workdays, the project team would use 12 workdays These additional two
days could really help the project team in getting the work completed on time.

Advantage of PERT

A PERT chart makes planning
large projects easier

PERT is a good way of making
these relationships visible in a diagram

PERT makes the critical path

Disadvantage of PERT

PERT charts can be
complicated and confusing, with hundreds or even thousands of tasks and
dependency relationships

PERT diagrams can be
expensive to develop, update and maintain.

PERT charts depend on the
ability to predict precise time frames for multitudes of tasks

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