I'll briefly explain by a homely analogy. Suppose your clan has designated you to schedule a gathering of all the relatives for a momentous anniversary on a given date. You write out the basic stages of issuing invitations, ordering food, checking on transportation, etc. Some of these stages precede others, while some stages must be simultaneously in development, so a skeleton PERT diagram is laid out. An estimate is made about the time to fulfill a given stage in order that the next stage "of this line" can be taken up.

Technically, there is a way of using what statisticians call "The Beta Probability Distribution" to estimate the probability that a given stage will be reached and completed. PERT especially emphsizes what is called "the critical path", or the several "critical paths". A critical path is one containing the lowest probability of attainment ON TIME: WHERE THE WHOLE PROGRAM COULD BREAK DOWN OR GET CRITICALLY OUT OF WHACK. CPA, or critical path analysis was studied and applied as a separate application, apart from PERT. Charlotte?

The most famous use of PERT was in monitoring the "Polaris Project" in the 60's -- producing the first nuclear submarine fleet for the Navy. Rear Admiral Radford, manager of this program, papered his office with PERT charts. And the project CAME IN AHEAD OF TIME! -- one of few cases, if not the only case, in which a defense project was this successful! This recommended PERT to the business and the academic world.

The second famous use of PERT was that made by the founders of XEROX, in planning to produce the first photocopier. PERT made it possible for Xerox to beat out all competitors, resulting in a historic rise on the Stock Market. Among other events, PERT (Program Analysis and Review Technique) and CPA (critical path analysis) warned Xerox supervisors about the critical activity of preparing copies of their PERT charts and the associated diagrams to fulfill a given critical path. Executives who had risen from mechanical drawing were pressed into service to develop diagrams; mail room clerks studying this subject in night school were drafted; secretaries or typists who had learned mechanical drawing from their fathers were drafted; etc; and the needed diagrams were prepared on time.

In 1962 I had developed a unique program for encouraging college math students to proceed at their own learning rate. While teaching a PERT course, I heard about the development at a hospital in Houston, TX, of MEDIPERT, monitoring the prognosis of patients. Using this as a model, I developed STUDYPERT, which allowed capable students to monitor their own completion of my mathematical study programs.

A VERION OF MEDI-PERT COULD BE ADAPTED TO DETERMINE THE PROSTHETIC PERIOD FOR A PARAMBIENT.