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:

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Duration       = 

And,

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.