2. path visible Disadvantage of PERT ·

 2. Program Evaluation and Review Technique  (PERT) PERT was initially used by defiance  in their Polaris project .In this method, theactivities time duration is found using  these following formula:Duration       =  And,Standard Devation    =       A network analysis method is used to approximateproject time duration when there is a unpredictabilityabout the individual activity time duration approximates.

PERT applies thecritical path method (CPM) to a weighted average time duration approximate.This approach was developed about the same time as CPM, in the late 1950s, andalso uses network diagrams concept, which are still sometimes referred to as PERTcharts. PERT uses probabilistic time approximates duration. Approximation basedon using optimistic time, most likely time , and pessimistic time  approximates of activity durations instead ofone specific or discrete duration approximate, as CPM does .By using the PERTweighted average for each activity duration approximate, the total projectduration approximate takes into account the risk or uncertainty in theindividual activity estimate.

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 For example:Suppose A project team in the project caseused PERT to determine the schedule for the online application registrationsystem project. They would have to collect data for the optimistic, mostlikely, 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 todo this activity. Without using PERT, the duration approximate for thatactivity would be 10 workdays.

Using PERT, the project team would also need to approximatethe pessimistic and optimistic times for completing this activity. Suppose anoptimistic approximate is that the input screen can be designed in eightworkdays, and a pessimistic time approximate is 24 workdays. Applying the PERT formula:PERT weighted average =                                                                                                  = 12Instead of using the most likely duration approximateof 10 workdays, the project team would use 12 workdays These additional twodays could really help the project team in getting the work completed on time. Advantage of PERT·        A PERT chart makes planninglarge projects easier·        PERT is a good way of makingthese relationships visible in a diagram·        PERT makes the critical pathvisibleDisadvantage of PERT·        PERT charts can becomplicated and confusing, with hundreds or even thousands of tasks anddependency relationships·        PERT diagrams can beexpensive to develop, update and maintain.·        PERT charts depend on theability to predict precise time frames for multitudes of tasks


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