The program evaluation review technique (PERT) is a project planning and control technique. It is an event oriented technique. It provides an approach for keeping planning up-to-date. It provides a way for management to require that planning be done on a uniform and logical basis. It permits management to foresee quickly the impact of variations from the plan. The program evaluation review technique is applied for long-range planning, installation of machinery, research and development of products and marketing programs and advertising programs. The PERT analysis is based upon the following three time estimates

(a) Optimistic time. It is the shortest possible time in which an activity can be completed if every thing goes exceptionally well.

(b) Most likely time. It is the time in which the activity is normally expected to complete under normal contingencies.

(c) Pessimistic time. It is the time which an activity will take to complete in case of difficulty.

It is the longest of all the three time estimates.