Monday, February 04, 2008

Estimate using probability curve

Programmers usually pick the earliest possible date when they are asked to estimate. Tom Demarco and Tim Lister make this observation with the probability distribution diagram. The area under the curve shows the probability from 1 to 100%. The most probable date of complete is August 9 and we are certain that 100% of the project will be complete by February 20. Tom Demarco and Lister refer to earliest possible point of completion, June 17 as the "nano-percent date". Nano date is the one that managers like and if you give them a range like this diagram it may not go well with them at all. This explains the fact that programmers estimates at Nano date and things always takes longer.

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