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# Is PERT technique Probabilistic or deterministic?

2 replies [Last post]
David Appelfeld
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Joined: 5 May 2008
Posts: 7
Dear planners

I am very new into planning and I am writing my master thesis about scheduling and risk management.
Can someone explain me if the PERT technique is probabilistic or just deterministic? I read some articles that say it is probabilistic, because the three estimates of time together determine the probability distribution of the completion time on the critical path. However, all the data are determined by the deterministic methods and all computed values are completely determined by the data used to compute them, therefore the duration time will be all the time same and doesn’t matter how many times do you calculate duration, it will be all the time same.

David

## Replies

Oliver Melling
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Joined: 24 Apr 2007
Posts: 595
Groups: The GrapeVine
David,

Use the Project Management Body of Knowledge as a primary source of information for your dissertation.

The two main ones are:

APM Body of Knowledge
PMI Body of Knowledge

Each have sections on Risk Management which you can use as a reference.Try governemnt website also, you will definately find something about project risk analysis/management.
Philip Rawlings
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Joined: 16 Nov 2004
Posts: 41
Groups: None
David
The PERT calculation takes minimum(A), most likely(B) and maximum(C) durations, calculates a working duration as (A+4B+C)/6 and doing a deterministic calculation. Then the single critical path is calculated a a rang one the end dates determined from the variances of the activities making up that single path. It is a simplistic approach dating from days when risk analyses calculation were computer-intensive and therefore expensive. It is largely unnecessary now given efficient and affordable risk analysis packages - e.g. Pertmaster www.pertmaster.com and www.primaver.com.

Hope that helps
Phil