1. Aim: Develop Timeline chart & project table using PERT/CPM Project scheduling
methods.
2. Objectives: From this experiment, the student will be able,
● To introduce the concept of advance software methodology
● To understand Project management software for scheduling, cost control and
budget management, resource allocation, collaboration software,
communication, quality management and documentation or administration
systems which are used to deal with the complexity of large projects .
3. Outcomes: The learner will be able to
● To apply the software concepts for implementation of Project Scheduling
● To understand, identify, analyze and design the problem, implement using
current techniques and skills.
4. Hardware / Software Required: PERT & CPM tools
5. Theory:
• Introduction
Basically, PERT (Programed Evaluation Review Technique) and CPM (Critical Path
Method) are project management techniques, which have been created out of the need
of Western industrial and military establishments to plan, schedule and control
complex projects.
• Planning, Scheduling & Control
Planning, Scheduling (or organizing) and Control are considered to be basic
Managerial functions, and CPM/PERT has been rightfully accorded due importance
in the literature on Operations Research and Quantitative Analysis. PERT/CPM
provided a focus around which managers could brain-storm and put their ideas
together. It proved to be a great communication medium by which thinkers and
planners at one level could communicate their ideas, their doubts and fears to another
level. Most important, it became a useful tool for evaluating the performance of
individuals and teams.
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There are many variations of CPM/PERT which have been useful in planning costs,
scheduling manpower and machine time. CPM/PERT can answer the following
important questions:
● How long will the entire project take to be completed? What are the risks
involved?
● Which are the critical activities or tasks in the project which could delay the entire
project if they were not completed on time?
● Is the project on schedule, behind schedule or ahead of schedule?
● If the project has to be finished earlier than planned, what is the best way to do
this at the least cost?
• The Framework for PERT and CPM
Essentially, there are six steps which are common to both the techniques. The
procedure is listed below:
I. Define the Project and all of its significant activities or tasks. The Project
(made up of several tasks) should have only a single start activity and a single
finish activity.
II. Develop the relationships among the activities. Decide which activities must
precede and which must follow others.
III. Draw the “Network” connecting all the activities. Each Activity should have
unique event numbers. Dummy arrows are used where required to avoid
giving the same numbering to two activities.
IV. Assign time and/or cost estimates to each activity
V. Compute the longest time path through the network. This is called the critical
path.
VI. Use the Network to help plan, schedule, and monitor and control the project.
The Key Concept used by CPM/PERT is that a small set of activities, which make up
the longest path through the activity network control the entire project. If these
“critical” activities could be identified and assigned to responsible persons,
management resources could be optimally used by concentrating on the few activities
which determine the fate of the entire project. Non-critical activities can be
re-planned, rescheduled and resources for them can be reallocated flexibly, without
affecting the whole project.
Five useful questions to ask when preparing an activity network are:
• Is this a Start Activity?
• Is this a Finish Activity?
• What Activity Precedes this?
• What Activity Follows this?
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• What Activity is Concurrent with this?
Some activities are serially linked. The second activity can begin only after the first
activity is completed. In certain cases, the activities are concurrent, because they are
independent of each other and can start simultaneously. This is especially the case in
organizations which have supervisory resources so that work can be delegated to
various departments which will be responsible for the activities and their completion
as planned. When work is delegated like this, the need for constant feedback and
co-ordination becomes an important senior management pre-occupation.
• Drawing the CPM/PERT Network
Each activity (or sub-project) in a PERT/CPM Network is represented by an arrow
symbol. Each activity is preceded and succeeded by an event, represented as a circle
and numbered.
At Event 3, we have to evaluate two predecessor activities – Activity 1-3 and Activity
2-3, both of which are predecessor activities. Activity 1-3 gives us an Earliest Start of
3 weeks at Event 3. However, Activity 2-3 also has to be completed before Event 3
can begin. Along this route, the Earliest Start would be 4+0=4. The rule is to take the
longer (bigger) of the two Earliest Starts. So the earliest Start at event 3 is 4.
Similarly, at Event 4, we find we have to evaluate two predecessor activities –
Activity 2-4 and Activity 3-4. Along Activity 2-4, the Earliest Start at Event 4 would
be 10 wks, but along Activity 3-4, the Earliest Start at Event 4 would be 11 wks.
Since 11 wks is larger than 10 wks, we select it as the Earliest Start at Event 4.We has
now found the longest path through the network. It will take 11 weeks along activities
1-2, 2-3 and 3-4. This is the Critical Path.
• The Backward Pass – Latest Finish Time Rule
To make the Backward Pass, we begin at the sink or the final event and work
backwards to the first event.
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At Event 3 there is only one activity, Activity 3-4 in the backward pass, and we find
that the value is 11-7 = 4 weeks. However at Event 2 we have to evaluate 2 activities,
2-3 and 2-4. We find that the backward pass through 2-4 gives us a value of 11-6 = 5
while 2-3 gives us 4-0 = 4. We take the smaller value of 4 on the backward pass.
• Tabulation & Analysis of Activities
We are now ready to tabulate the various events and calculate the Earliest and Latest
Start and Finish times. We are also now ready to compute the SLACK or TOTAL
FLOAT, which is defined as the difference between the Latest Start and Earliest Start.
Event Duration(Weeks) Earliest
Start
Earliest
Finish
Latest
Start
Latest
Finish
Total
Float
1-2 4 0 4 0 4 0
2-3 0 4 4 4 4 0
3-4 7 4 11 4 11 0
1-3 3 0 3 1 4 1
2-4 6 4 10 5 11 1
▪ The Earliest Start is the value in the rectangle near the tail of each activity
▪ The Earliest Finish is = Earliest Start + Duration
▪ The Latest Finish is the value in the diamond at the head of each activity
▪ The Latest Start is = Latest Finish – Duration
There are two important types of Float or Slack. These are Total Float and Free Float.
• Total Float is the spare time available when all preceding activities occur at the
earliest possible times and all succeeding activities occur at the latest possible
times.
Total Float = Latest Start – Earliest Start
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• Activities with zero Total float are on the Critical Path. Free Float is the spare
time available when all preceding activities occur at the earliest possible times and
all succeeding activities occur at the earliest possible times.When an activity has
zero Total float, free float will also be zero.
• There are various other types of float (Independent, Early Free, Early Interfering,
Late Free, Late Interfering), and float can also be negative. We shall not go into
these situations at present for the sake of simplicity and be concerned only with
Total Float for the time being.
• Having computed the various parameters of each activity, we are now ready to go
into the scheduling phase, using a type of bar chart known as the Gantt chart.
• There are various other types of float (Independent, Early Free, Early Interfering,
Late Free, Late Interfering), and float can also be negative. We shall not go into
these situations at present for the sake of simplicity and be concerned only with
Total Float for the time being. Having computed the various parameters of each
activity, we are now ready to go into the scheduling phase, using a type of bar
chart known as the Gantt chart.
6. Procedure:
Students should define activities planned for their case study & use PERT & CPM
Method to draw Timeline chart & project table
7. Conclusion:
A Timeline chart& project table helps in planning, how long that project might take
and that can really save time in the end and more so if you are on a deadline
8. Viva Questions:
1. What are the components of timeline chart?
2. Explain critical path method in detail.
9. References:
1. www2.kimep.kz/bcb/omis/our_courses/is4201/Chap14.pdf
2. https://www.youtube.com/watch?v=zC2ji72DxXg
3. www.slideshare.net/koppulachandra/cpm-pert-problems
4. https://www.youtube.com/watch?v=LdRZN5o)8eM
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