Significance of
Normal Distributed Output Milestone
The significance of the fact that the output milestone is
approximately Normal distributed is not trivial. Here is why. Given the symmetry
of the Normal curve, a Normal distributed output milestone means there is just
as likely a possibility that the schedule will underrun (complete early) as
overrun (complete late). Confronted with such a conclusion, most project
managers would say: "No! The schedule is
biased toward overrun." Such a reaction simply means that either the schedule is
too short and the Normal output milestone is too aggressive, or the project
manager has not thought objectively about the schedule risk.
Consider this conclusion about a Normal output milestone from
another point of view. Without even considering what the distributions of the
individual tasks on the WBS might be, whether BETA or Triangular or Normal or
whatever, the project manager remains confident that the output milestone is
Normal in its distribution! That is to say that there is a conclusion for every
project, and it is the same conclusion for every project — the summation
milestone of the critical path is approximately Normal. [3]