PERT

PERT (Program Evaluation and Review Technique) was developed in 1958 to help measure and control the progress of the Polaris Fleet Ballistic Missile program. The technique earned considerable respect for assisting in the management of thousands of different contractors and agencies, and is credited with helping to advance the completion date of the program by two years PERT is a technique for estimating and planning a large project. One of its most powerful concepts is that project management is the management of probabilities. PERT makes use of simple statistical mathematics in order to come up with a probability distribution for the completion dates of the project milestones.For example, in PERT tasks are estimated with three numbers: The best case, the nominal case, and the worst case. These three estimates are combined into an expected duration, and a standard deviation. Thus the duration of each task is presumed to be a random variable with a known distribution. The math is very simple. Consider a task whose best/nominal/worst estimate is 3/5/9. The expected completion time (µ) is assumed to be (4*nominal + best + worst)/6, or in our case (4*5+3+9)/6 or about 5.33. The standard deviation (s) is assumed to be (worst - best)/6 or (9-3)/6 or 1. Now consider a simple project consisting of three tasks. We represent this as a simple chart with circles and arrows. The circles denote events, and the arrows denote tasks