Three-point estimation: Difference between revisions

Revision as of 19:47, 7 March 2009

Revision as of 20:19, 24 April 2009

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The '''three-point estimation''' technique is based on statistical methods, and in particular, the [[normal distribution]]. Three-point estimation is the preferred estimation technique for [[Information Systems]] (IS) projects. In the three-point estimation wethere produceare three figures produced for every estimate:

* ''a'' = the best-case estimate

* ''m'' = the most likely estimate

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To produce a project estimate the project manager:

* Decomposes the project into a list of estimable tasks, i.e. a [[Work Breakdown Structurebreakdown structure]]

* Estimates each the E value and SD for each task.

* Calculates the E value for the total project work as E (Project Work) = Σ E (Task)

* Calculates the SD value for the total project work as SD (Project Work) = √Σ SD (Task) 2

We then use theThe E and SD values are then used to convert the project estimates to Confidence Levels as follows:

* Confidence level in E value is approximately 50%

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* Confidence level in E value + 2 × SD is approximately 95%

* Confidence level in E value + 3 × SD is approximately 99.5%

* IS useuses the 95% confidence level, i.e. E Value + 2 × SD, for all project and task estimates

== See also ==

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[[Category:Statistical approximations]]

[[de:Drei-Zeiten-Methode]]

{{Statistics-stub}}