Why 6?
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Its a weighted average. The 4 and 6 are related to each other in that you have 4 parts of one element and 1 part each of two other elements for 6 total parts. The equation could just as easily have 6/8 instead of 4/6 if the probable estimate was deemed to have a higher weight.
I do not know why 4/6 is generally used as opposed to 6/8, 10/12 or any other weighting factor.
Stacy
Project Management Knowledge Base
Hello,
This is related to the theory of probability.
The graph generated is a bell shape.
The equation is similar to mean average.
I hope you understand and recall your mathematics or higher algebra, differential calculus, intergral calculus, engineering mathtmatics or any subject related to mathematics.
Cheers,
Charlie
Where
a = pessimistic duration
4m = 4 * probable duration
b = optimistic duration
generally accepted "rule of thumb". You could equally propose your own method.
(((a+b)/2)+m)/2) for instance