PERT duration times: Mathematics or MBO?

The authors examine and compare the origins and mechanics of program evaluation and review technique (PERT) and management by objectives (MBO), reviewing the controversy concerning the mathematical validity of PERT activity duration estimates; the mathematics appear to be of little practical significance. It is the estimation process that is important, and this PERT estimation process is much like the objective development process of MBO. Definite similarities exist. PERT could be considered an extension of MBO.