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Test Estimation Techniques - Three Point Estimation

Written by  Ritu Saxena | 19 March 2012
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estimationGone are the days when the software testing used to be an additional role and responsibility of the developer. The complexity and size of the software has increased multi-fold and with that the types of testing and complexity of testing has also increased.


It is based on statistical methods in which each testing task is broken down into sub tasks and then three types of estimation are done on each tasks. The first number is the best case estimate; i.e., assume everything goes well. The second number is the worst-case estimate; i.e., assume our worst fears are realized. The third number is the expected-case estimate. The average of the expected cases is the final estimate, but the best case and worst-case estimates are documented to understand the accuracy of the estimate and to feed into the test planning and risk management processes.

The formula used by this technique is:

Test Estimate = P + (4*N) + E / 6

Where P = Positive Scenarios, N = Negative Scenarios, E = Exceptional Scenarios
Standard deviation for the technique is calculated as,
Standard Deviation (SD) = (N – E)/6

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Ritu Saxena

Ritu Saxena

Ritu is the technical brain behind the website and comes from a strong development background across Web and Mobile platforms. She is our senior editor primarily responsible for Product Reviews and in future will be leading Start-Ups, Mobile and Quality areas.

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