Network Diagrams, PERT & CPM, Practice

with MS Project

Lecture (6 & 7)

Mr. Mubashir Ali Lecturer(Dept. of Computer Science)

dr.mubashirali1@gmail.com

PROJECT

Combination of interrelated activities

Executed in logical sequence

Accomplishment of a desired objective

“A project is a temporary

effort undertaken to create a

"unique" product or service”

Plan your work first…..then work your plan

HISTORY OF PERT/CPM

Developed by the US Navy for the planning and control of the Polaris missile program

The emphasis was on completing the program in the shortest possible time.

PERTDeveloped by Du Pont to solve project scheduling problems

The emphasis was on the trade-off between the cost of the project and its overall completion time

CPM

Why PERT/CPM?

Prediction of deliverables

Planning resource requirements

Controlling resource allocation

Internal program review

External program review

Performance evaluation

Uniform wide acceptance

APPLICATIONS OF PERT/CPM TECHNIQUES

SPM

• Construction of a Dam or Canal

• Construction of a building or highway

SPM

• Maintenance of aircrafts

• Space Flights

SPM

• Designing a Prototype of a Machine

• Development of Supersonic Planes

Steps in PERT/CPM

4. CONTROLLING

3. ALLOCATION OF RESOURCES

2. SCHEDULING

1. PLANNING

Framework for PERT and CPM

Define the Project. The Project should have only a

single start activity and a single finish activity.

Develop the relationships among the activities.

Draw the "Network" connecting all the activities.

Assign time and/or cost estimates to each activity

Compute the critical path.

Use the Network to help plan, schedule, monitor and

control the project.

CPM - Critical Path Method

Drafting the design of Program or Project

Evaluation of drafted Program or Project

Review of evaluated Program or Project

PERT - Project Evaluation & Review Techniques

To analyze and represent the tasks involved in completing a given project

Accommodates the variation in event completion time

Event-oriented technique rather than start- and completion-oriented

Commonly used in conjunction with the critical path method

Basic Terms In Network Analysis

Activity

Event

Constraints

Network Diagram

Critical Path

Network Diagram

Concepts

Activity

Precedence relationship

Successor

Event

Guidelines for network diagram

1. Before an activity can begin, its preceding activities must be completed.

2. Arrows indicate logical precedence.

3. Flow of the diagram is from left to right.

4. Arrows should not intersect.

5. Dangling should be avoided.

APPRAOCHES FOR NETWORK DIAGRAMACTIVITY ON ARC(AOA):

Uses arcs to represent activities and nodes to represent events.

It is Event Oriented.

1 876

54

3

2

DUMMY ACTIVITY

AOA approach requires the addition of a Dummy Activity to

clarify the precedence relationships between the two activities.

It is a zero time activity and consumes no resources.

Dummy Activity is used in two situations:

1. When two or more activities start and end at the same nodes.

1 3

2

2) When two or more activities share the sameprecedence activity but not all the precedenceare shared.

1 53

6

7

2 4

Continued..

Uses nodes to represent activities and arcs indicate

precedence relationships between them.

It is Activity Oriented.

ACTIVITY ON NODE(AON):

ESTIMATING TIME OF COMPLETION

Planning the schedule of the projectTime estimates include:

1) Total time for completion.

2) ES- Earliest start time: the earliest time at which the activity can start given that its precedent activities must be completed first.

3) EF-Earliest finish time: equals to the earliest start time for the activity plus the time required to complete the activity.

4) LF- Latest finish time: the latest time in which the activity can be completed without delaying the project.

5) LS- Latest start time: equal to the latest finish time minus the time required to complete the activity.

6) FORWARD PASS: The early start and early finish timesare calculated by moving forward through the network andconsidering the predecessor activities Considers maximum

7) BACKWARD PASS: The latest start and finish times arecalculated by moving backward through the networkConsiders minimum.

8) SLACK TIME: Slack time for an activity is the differencebetween its earliest and latest start time or between theearliest and latest finish time. Critical path is the path ofactivities having zero Slack time.

Continued..

Errors in Network Construction

Dangling

3 4 6 8

5

7

Dangling

Looping

4 5 9

7

6

8

Looping

Redundancy

5

6

7Redundancy

Comparison Between PERT & CPM

Both are Quantitative Techniques of Network Analysis

Both are used as tools for Decision Making

Both involve drawing & analysis of Network Diagram on various scores

Difference Between PERT & CPM

Probabilistic Model

Non-repetitive Jobs like planning & scheduling of

programmes

Results calculated on basis of Events

Related with activities of uncertain time

Deterministic Model

Repetitive Jobs like residential construction

Results calculated on basis of activities

Related with activities of Well Known time

PERT CPM

Advantages of PERT/CPM

Reduction in cost

• Elimination of Risk in Complex activity

Flexibility

• Optimization of Resources

Reduction of Uncertainties

Disadvantages of PERT/CPM

Network charts tend to be large

Lack of a timeframe on most PERT/CPM charts makes it harder to show status

When PERT/CPM charts become unwieldy, they are no longer used to manage the project

Planning & Implementation required skillful personnel

References & Assignment

• Introduction to Operations Research 7th

Edition by Hillier & Lieberman (Chapter-10)

• Install MS-Project and build your Final Year

Project structure by using ‘SOW’ and ‘WBS’.

• For better understanding of MS-Project

working, follow any tutorial from YouTube.