The full form of PERT is Project Evaluation and Review Technique. The PERT methodology has been developed by the United S Naval forces . In PERT , three parameters are tracked:

- Optimistic estimate
- Pessimistic estimate
- Most likely estimate

These three are then combined and a best estimate is found using the following formula:

PERT Estimate = (Optimistic Estimate + Pessimistic estimate +**4 *** Most Likely estimate) **÷ 6 **

So each of the item that needs to be estimated , are deliberated upon and three kinds of estimates are sought.

- Optimistic estimate of time, which is the time that will take to complete the requirement when everything leading to the requirement works fine and its envisaged that that no obstacles will be faced , in terms of resources , processes or technical
- Pessimistic estimate of time , which is the time that will take to complete the requirement when every obstacle that’s possible leading to the requirement is encountered in terms of resources , processes or technical
- Given that in life everything is a mix of good and bad , so most likely estimate should take into account some positives and some negatives that can be encountered , so in terms of time this will be more than the Optimistic and will be less than the Pessimistic.

An example of practically using the technique is given below: Each of the three user requirements have been estimated for optimistic ,

pessimistic and most likely values, and then using the PERT formula the most realistic estimate has been calculated. To fully exploit the benefits of PERT, Critical Path Method or CPM should be used.

From the chart given here , we see three PERT values have been derived. However , how do we know that the different values are good enough? We have to know about Standard Deviation to know that.

* -By Mala Bose . Google+*

Copyright QA Friend Software Testing. All rights reserved.