Network Techniques

NAME : AVULA ANIL KUMAR
ROLL NO : 1007-15-508-010
SUBJECT : APPLIED STATISTICS
SEMISTER : III
TOPIC : Network Techniques
3 December 2016

CPM and PERT Network techniques
3 December 2016

Contents
 INTRODUCTION
 DEFINITIONS OF PROJECT AND PROJECT MANAGEMENT
 NETWORK PLANNING METHODS
 WHAT IS NETWORK
 CONSTRUCTION OF NETWORK
 CPM
 PERT
 CPM VS PERT
3 December 2016

INTRODUCTION
 To perform any job optimally we should have some planning
 Generally planning and performing job is called project.
 The project requires some techniques to done the project
 Those are CPM and PERT
3 December 2016

Definitions
Project:
 project is a group or combination of activities that must be executed in a certain
fixed order before entire task is completed.
 The projects are non-repetitive large tasks
Project management:
 Project management is a scientific way of planning, implementing, monitoring &
controlling the various aspects of a project such as time, money, materials,
manpower & other resources.
3 December 2016

Real time example for a project
 Project: Getting ready to attend the college
 Wake up in the Morning
 Brush your teeth
 Take bath
 Wear formal dress
 Take break fast
 Walk to the college
 These are the basic activities we need to complete for accomplishment of project.
3 December 2016

Network Planning methods
 Methods used for network planning are:
 CPM
 PERT
 Managing a project with network planning methods involves four steps:
 Describing the project.
 Diagramming the Network.
 Estimating time of completion.
 Monitoring project progress.
3 December 2016

Network Diagram
 Network:
Network is a graphical representation of a project operations and it is
composed of several activities and events which are inter-related.
 Network consists of:
 Event
 Activity
3 December 2016

Basic Building blocks of Network
 Activity:
Activity is a recognizable part of the project which consume time and resources for its
completion.
In network diagram “ARROW” represents activity
 Critical activity
 Dummy activity
 Event:
An event represents the accomplishment of some task. In a network diagram,
beginning and ending of an activity represented by an event.
In network diagram “NODE” represents event.
 Merge event
 Burst event
3 December 2016

Construction of a Network
Rules for drawing network diagram
1. Each activity is represented by one and only one arrow in the network
2. No two activities can be identified by the same end events
3. Before an activity can begin, it preceding activities must be completed.
4. Arrows indicate logical precedence.
5. Flow of the diagram is from left to right
6. Arrows should not intersect.
7. Dangling should be avoided.
3 December 2016

Activity Precedence
A --------
B --------
C A
D B
E A
F B
G C,D
H G,F
I E
J H,I
K J 3 December 2016

CPM
 CPM means “critical path method”.
 It is a network technique used to evaluate the project.
 If the activity times are deterministic then critical path method can be used as a
systematic method.
 CPM evaluates project by determining critical path in the network.
3 December 2016

Critical Path
 Critical path is the longest path in the network from the starting event to ending
event
 Critical path defines minimum time required to complete the project
 In network diagram critical path is represented with double arrows
 Critical path consist:
 Critical event: The events with zero slack
 Critical activity: The activities with zero total float
3 December 2016

Network of CPM
 Earliest Activity start time(EST)
The earliest start time that an activity can be started
 Earliest Activity finish time(EFT)
EFT= EST + Duration
 Latest Activity finish time(LFT)
 Latest Activity start time(LST)
LST= LFT-duration
3 December 2016

Types of Float
 Total float
(TF)ij = (Lj – Tij)- Ei
 Free float
(Ff)Ij =Total float – ( Lj- Ej)
 Independent float
(If)ij = Free float- Tail event slack
Tiji j
Ei Ej
Li Lj
3 December 2016

Draw network diagram and analyzing CPM
Activity Immediate
predecessor
Duration
(months)
A -------------- 2
B -------------- 5
C -------------- 4
D B 5
E A 7
F A 3
G B 3
H C,D 6
I C,D 2
J E 5
K F,G,H 4
L F,G,H 3
M I 12
N J,K 8
3 December 2016

PERT
 PERT means project (or) programme Evaluation & Review Technique.
 When activity times are probabilistic, PERT is an effective tool for evaluate
project.
 PERT is associated with 3 time estimates
 Optimistic Time ( to)
 Pessimistic Time ( tP)
 Most likely Time ( tm)
3 December 2016

Activity Times in PERT
 Optimistic Time: ( To)
It is the minimum time that is required to complete an activity when every
resource is available
 Most likely Time: (Tm)
This is the time required for the completion of activity under normal conditions.
 Pessimistic Time: (Tp)
The most time that is required to complete activity when every resource is not
available
Note: In PERT β – distribution is used to represent these three time estimates
3 December 2016

Formulae used for evaluation of PERT
 Time estimate (Te)=
𝑇𝑜+𝑇𝑝+4𝑇𝑚
6
 Standard deviation ( )= 𝑇𝑝 −𝑇𝑂
6
 Variance =
𝑇𝑝−𝑇𝑜 2
36
3 December 2016

CPM VS PERT
CPM PERT
It is activity oriented It is event oriented
It is associated with deterministic activities It is associated with probabilistic activities
It is based upon single time to complete
an activity
It is based upon 3 time estimate to
complete an activity
It is used mainly for construction project It is used mainly for research and
development project
3 December 2016

References
3 December 2016
1. Wikipedia
2. Mechanical engineering Ace material
3. Some of the YouTube videos

Network Techniques

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