Why 6?

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

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

It’s 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