This document provides information on the project management techniques of PERT and CPM. It defines PERT as dealing with uncertain project activities, using three time estimates and a probabilistic model. CPM is described as handling well-defined activities with fixed durations, using a deterministic model and focusing on time-cost tradeoffs. The document also outlines key elements of each technique such as events and activities, the critical path, and float.

1. PERT & CPM
SHASHWATVISHWAKARMA
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 ReviewTechnique (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 ReviewTechnique, 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. TECHNICALTERMS 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) DUMMYACTIVITY
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.
■ Event 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 STARTTIME (E.S.T.)
The earliest possible time at which an activity may start, is called early start time.
(6) EARLY FINISHTIME (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 STARTTIME (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 FINISHTIME (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) CRITICALACTIVITIES
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