cpm and pert project mangement techniques, Exams of Project Management

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NETWORK TECHNIQUES - CPM & PERT

NETWORK TECHNIQUES - CPM & PERT

Presented by:

Vivek Dahiya 19137

Content

Introduction

Steps involved in PERT & CPM

Network principles

Approaches for network diagram

Rules for construction of network

diagram

Sample question- CPM & PERT

Summary

CPM-CRITICAL PATH METHOD

HISTORY :

It was developed independently in 1956-57 by Du Pont company in

US to solve trade off cost of project and it over all completion

time (scheduling problems).It was applied to construction of

chemical plant

DEFINITION :

Critical path is the sequence of activities between a project’s start

and finish

that takes the longest time to complete.

Applied to projects that employ stable technology and

relatively risk free

Hence the orientation is “DETERMINISTIC “

PERT-PROGRAM EVALUATION REVIEW TECHNIQUE

HISTORY

Originally develop to facilitate the planning and scheduling

Polaris fleet Ballistic Missile Project of US government.

DEFINATION:

It deals with activities whose duration is not exactly known, it

relies upon pessimistic time, optimistic time and most probable

time.

It helps to find out the variance in the path of project.

Used for risk and uncertain situation

Used for research and development program, aerospace

project

Project involving new technologies

Projects with variable completion time

Hence the orientation of PERT is PROBALISTIC

STEP INVOLVED IN PERT & CPM

Steps involved are :

1. Identify the specific activities.

2. Determine proper sequence of the activities.

3. Construct the network diagram.

4. Estimate the time required for each activity.

5. Determine the critical path , slack.

6. Development of project schedule

7. Calculate the variability of project duration and probability

of completion in given time(Update the PERT chart.)

NETWORK PRINCIPLES

ACTIVITY - An activity is a definite task ,job, or function to be performed in a project

E.g. – “Prepare dinner “is an activity

 An activity is represented by an arrow

 The head of the arrow marks the completion of the activity

and the tail of the arrow marks the beginning.

 The length and direction of arrow as no significance.

• Merge activity – an activity which is dependent on two or more preceding activities
• Burst activity- an activity that is followed by two or more activities.
• Path- a path is unbroken chain of activities from initiating node to some other

node(last)

EVENT - describe the start and the completion of the an activity.it is donated by the

number

An event is specific point of time indicating the beginning and the end of one

or more activities.

APPRAOCHES FOR NETWORK

DIAGRAM

ACTIVITY ON ARROW (AOA):

Uses arrow to represent activities and nodes to represent

events.

It is Event Oriented.

Dummy activity :is required when two or more activities start

from single node and end in single node

1 6 7 8

4 5

3

2

A

B

C

E

D

F

G H

Dummy

Uses nodes to represent activities indicate precedence

relationships between them.

It is Activity Oriented.

ACTIVITY ON NODE(AON):

TIME ESTIMATES

Once the logic and details of the network has been established

time estimates are assigned-

Optimistic time(a )-It is the shortest time in which the

activity can be completed.

Most probable time/likely time (m) -It is the probable

time required to perform the activity.

Pessimistic time (b)- it is longest estimated time.

Average time(expected time ) = a+4m*b

CPM & PERT – sample Question

Sta

rt

A

A

B

C

D

D

E

E

F

Level

Level

Level

G

G

H

H I

I

J

J

en

d

Level

Level

level

Each activity have preceding and

succeeding event.

Before an activity can begin, it

preceding activity must be

completed.

Each event should have distinct

number in way that head of arrow is

greater than the tail.

Length and direction of the arrow

has no significance.

Flow is from left to right

Arrow should not intersect.

There should be no loop in the

project network

Not more than one activity can have

same preceding and succeeding

events. Each activity is represented

by unique numbered arrow

3- construction of network diagram

KEY

It defines what format we are using

It act has reference

A

ES EF

D

SLACK

LS LF

ES- earliest start time

EF-earliest finish time

LS-latest start

LF latest finish

D-duration

6) FORWARD PASS:

The early start and early finish times are calculated by

moving forward through the network considering the predecessor

activities.

Considers maximum

7) BACKWARD PASS:

The latest start and finish times are calculated by moving

backward through the network.

Considers minimum

8) SLACK TIME:

Slack time for an activity is the difference between its earliest and

latest start time or between the earliest and latest finish time.

9) Critical path- is the path of activities having zero Slack time.

A

F

J

G

D

H

E

B

C

I s t a r t

E

n

d

PERT DIAGRAM & KEY