PERT and CPM

Project Evaluation and Review Technic and Critical Path Method are the effective methods to determining the estimated time for the completion of activities and tasks of a given project.Optimistic time, pessimistic time and most likely time using beta distribution ( bell shaped curve) of Research Methodology.

1. PERT & CPM SHASHWAT VISHWAKARMA 1304

2. Introduction Project management can be understood as a systematic way of planning, scheduling, executing, monitoring, controlling the different aspects of the project, so as to attain the goal made at the time of project formulation. PERT and CPM are the two network based project management techniques, which exhibit the flow and sequence of the activities and events.  Program (Project) Management and Review Technique (PERT)  is appropriate for the projects where time needed to complete different activities are not known. Critical Path Method  or  CPM , is apt for the projects which are recurring in nature.

3. PERT PERT is an acronym for Program (Project) Evaluation and Review Technique, in which planning, scheduling, organising, coordinating and controlling of uncertain activities take place. The technique studies and represents the tasks undertaken to complete a project, to identify the least time for completing a task and the minimum time required to complete the whole project . It is aimed to reduce the time and cost of the project.

4. PERT uses time as a variable which represents the planned resource application along with performance specification . In this technique, first of all, the project is divided into activities and events. After that proper sequence is ascertained, and a network is constructed. After that time needed in each activity is calculated and the critical path (longest path connecting all the events) is determined.

5. CPM Developed in the late 1950’s, Critical Path Method or CPM is an algorithm used for planning, scheduling, coordination and control of activities in a project. Here , it is assumed that the activity duration are fixed and certain. CPM is used to compute the earliest and latest possible start time for each activity . The process differentiates the critical and non-critical activities to reduce the time and avoid the queue generation in the process. The reason behind the identification of critical activities is that, if any activity is delayed, it will cause the whole process to suffer. That is why it is named as Critical Path Method.

6. CPM In this method, first of all, a list is prepared consisting of all the activities needed to complete a project, followed by the computation of time required to complete each activity . After that, the dependency between the activities is determined. Here, ‘path’ is defined as a sequence of activities in a network. The critical path is the path with the highest length.

7. TECHNICAL TERMS USED IN C.P.M [CRITICAL PATH METHOD]  ACTIVITY An activity is a part of the project denoted by an arrow on the network. The tail of the arrow indicates the start of the activity whereas the head indicates the end of the activity. One and only one arrow is used to represent one activity of given duration. The arrows of the activities are not drawn to scale. The durations of the activities are written along their arrows.

8. (2) DUMMY ACTIVITY The activity which neither uses any resources nor any time for its completion is called dummy activity. It is represented by a dotted arrow or a solid arrow with zero time duration. (3) EVENT Event is the stage or point where all previous jobs merging in it are completed and the jobs bursting out are still to be completed.

9. See the figure shown below- Event 1 is the starting point of the project. E vent 6 is the point where activities B(3), F(3), H(2) and K(5) merge and activity L(4) bursts. Events are generally represented by circles or nodes at the junctions of arrows. Events are serially numbered in their sequential order.

10. (4) NETWORK The diagrammatic representation of the activities of the entire project is called network of flow diagram. On this diagram various jobs of the project are shown in the order in which these are required to be performed . (5) EARLY START TIME (E.S.T .) The earliest possible time at which an activity may start, is called early start time . (6)  EARLY FINISH TIME (E.F.T .) The sum of the earliest start time of an activity and the time required for its completion is called early finish time.

11. (7) LATE START TIME (L.S.T.) The latest possible time at which an activity may start without delaying the date of the project, is called late start time. (8)  LATE FINISH TIME (L.F.T.) The sum of the late start time of an activity and the time required for its completion is called late finish time. (9 )  TOTAL FLOAT The difference between the maximum time allowed for an activity and its estimated duration is called total float. It is the duration of time by which the activity can be started late, without disturbing the project schedule. It is generally denoted by  S .

12. (10)  FREE FLOAT The duration of time by which the completion time of an activity can be delayed without affecting the start of succeeding activities is called free float. It is generally denoted by  S.F . (11)  CRITICAL ACTIVITIES The event which has no float, are called critical activities. The critical events are required to be completed on schedule. (12) CRITICAL PATH The path in the network joining the critical events is called the critical path of the work.

13. Comparison between PERT and CPM PERT CPM PERT is a project management technique, used to manage uncertain activities of a project. CPM is a statistical technique of project management that manages well defined activities of a project. A technique of planning and control of time. A method to control cost and time. Event-oriented Activity-oriented Evolved as Research & Development project Evolved as Construction project Probabilistic Model Deterministic Model Time Time-cost trade-off Three time estimates One time estimate