PERT (method for estimating)
Program
Evaluation and
Review
Technique
I first ran into PERT a couple years ago. Any “well known” methodology catches
my attention. I questioned the validity of this method for estimating at first but later realized it is fairly accurate on projects with many activities. I’m not sure you can expect accuracy on a single activity.
Wikipedia “PERT is a method to analyze the tasks involved in completing a given project, especially the time needed to complete each task, and identifying the minimum time needed to complete the total project.”
The premise is the majority of time lost and time saved for unexpected activity performance can be anticipated. The most optimistic view is weighted against the most pessimistic view then both are tempered by the most likely scenario weighted four times more than the others.
There is no magic or mysticism involved. If there is any magic it is the expert judgment required by the person estimating the activity.
Optimistic - shortest time in which the activity can be completed.
Most likely - highest probability guess.
Pessimistic - longest that might be required.
FORMULA:
Optimistic + (4 x Most likely) + Pessimistic
Estimate = -----------------------------------------------------------
6
