Critical Path Method & Network Analysis

Critical Path Method

&Network Analysis

Soc 3210 : Project Designing and Management

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Presentation Summary..

Critical Path Method

• Project Management • Critical Path• Critical Path Method (CPM)• Origin of CPM• Why CPM is Important• Terms Related to CPM• Procedure of CPM• Example• Advantages/Disadvantages

• Network Analysis

• Network• Network Analysis• Terms related to Network Analysis• Activity-on-Arc (AOA) Network• Concurrent Activities• Dummy Activities• Example

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What is Project Management??

Project management is the discipline of initiating, planning, executing, controlling, and closing the work of a team to achieve specific goals and meet specific success criteria.

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What is Critical Path??

• The sequence of project activities which add up to the longest overall duration.

• The critical path determines the shortest time possible to complete the project.

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What is Critical Path Method??

• Critical Path Method (CPM) is basically a step-by-step Project Management technique that separates planning and scheduling.

• It also clarifies the inter relationship of time and cost.• CPM evaluates all the

possible alternative plans for project and associates each plans with a schedule.

• It is a mathematical based algorithm for scheduling a set of project activities.

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The origins of CPM

• The CPM was developed in the 1950s by Morgan R. Walker of DuPont (Chemical Company) and James E. Kelley Jr. of Remington Rand (Machines Manufacturer).

• It was first used in a missile-defense construction project.• Since that time, the CPM has been adapted to other fields

including hardware and software product research and development.

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Where is it used??

And many more…

PROJECTS

Software Development

Construction

Aerospace & Defense

Research Projects

Product Development

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Why CPM is important??

• According to Dr. Larry Bennett (1978), the critical path method also has three main benefits for project managers. They are…

Identifies the Most Important Tasks

Helps to Reduce Timelines

Compares Planned with Actual

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Key Steps in the Critical Path Method...

• There are six key steps in the critical path method. They are..

Specify Each ActivityStep 1

Draw the Network DiagramStep 3

Establish Dependencies (Activity Sequence)Step 2

Update the Critical Path Diagram to Show

ProgressStep 6

Identify the Critical Path Step 5

Estimate Activity Completion Time Step 4

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• Step 1 : Specify Each Activity• The first step is to identify the main deliverables of a

project. Then you can start breaking down the high-level activities into smaller chunks of work.

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• Step 2 : Establish Dependencies (Activity Sequence)• Some activities will depend on the completion of others.

Listing the immediate predecessors of each activity will help you identify the correct order.

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• Step 3 : Draw the Network Diagram• Once you have identified the activities and their

dependencies, you can draw the critical path analysis chart (CPA), known as the network diagram.

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• Step 4 : Estimate Activity Completion Time• Using past experience or the knowledge of an experienced

team member, you must now estimate the time required to complete each activity. If you are managing a smaller project, you will most likely estimate time in days. If you are working with a complex project, you may have to measure time in weeks.

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• Step 5 : Identify the Critical Path• There are two ways you can now identify the critical path.

1. You can eyeball your network diagram and simply identify the longest path throughout the network (in terms of longest duration in days).

2. You can also identify critical activities with the Forward Pass/Backward Pass technique, identifying the earliest start and finish times, and the latest start and finish times for each activity.

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• Step 6 : Update the Critical Path Diagram to Show Progress

• As the project progresses, you will learn the actual activity completion times. The network diagram can then be updated to include this information (rather than continuing to use estimations).

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Terms Related to CPM

• Float(slack): It is the amount of time an activity can be delayed without delaying the project.

• Crashing: Reducing a project’s duration is called crashing.• Critical activity: Activity with zero float.• Resource leveling: It is an iterative process of assigning

crews to activities in order to calculate their duration.

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Calculation of CPM

• Earliest Start Time (EST)• Earliest Finish Time (EFT)• Latest start time (LST)• Latest Finish Time (LFT)• The longest path of planned

activities to the end of the project.

• The earliest and latest that each activity can start and finish without making the project longer.

• We have to determine “critical” activities.

• Crashing the critical path.

Need to find the following for each activity:

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Class Exercise..

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Example..

• Orange Square: Calculated Value

• White Circle: Duration

• Black hexagon: Crashing Value

• Critical Path: A-C-G-H

A C

START

G

B D E

H7

3

6 3

F

3 3

2 3

2

2

713

16

3 6

5

9

1816

137

0

16

13

13

10

0

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Advantages of CPM

• Consistent framework for planning, scheduling, monitoring, and controlling project.• Helps proper communications between departments and

functions.• Determines expected project completion date.• Determines the dates on which tasks may be started or

must be started if the project is to stay in schedule.• Shows which tasks must be coordinated to avoid

resource or timing conflicts.• Shows which tasks may run in parallel to meet project

completion date.

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Disadvantages of CPM

• Reliability of CPM largely based on accurate estimates and assumptions made.

• CPM does not guarantee the success of project. • Resources may not actually be as flexible as management

hope when they come to address network float.• Too many activities may the network diagram too

complicated.• Activities might themselves have to be broken down into

mini projects.

Network Analysis

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What is Network??

Any system of interconnected linear features..

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What is Network Analysis??

• Network Analysis is a technique for planning and controlling large projects, such as construction work, Research & Development projects, computerization of systems etc.

• Its primary aim is to program and monitor the progress of a project so that the project is completed in the minimum time. In doing this, it pinpoints the parts of the project which are “crucial”.

• It can also be used in allocating resources such as labor and equipment and thus helps to make the total cost of a project minimum.

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Network Analysis Methods

• Network Analysis methods is a group of special analytical methods that are used in cases where it is necessary to analyze and optimize a network of interconnected and related elements that have some connection between one another.

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Basic Network Analysis Methods

• CPM (Critical Path Method)• CCM (Critical Chain Method)• PERT Method (Program Evaluation and Review Technique)• GERT Method (Graphical Evaluation and Review Technique)• MPM Method (Metra Potential Method)

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Terms related to Network Analysis

• WBS: Break down the project into constituent activities such that each activity is clearly identifiable and manageable

• Activity: This is a physically identifiable part of the project that consumes time and resources. It is represented by an arrow (in AOA diagrams)

• Events (node): These are the beginning or end points of an activity. Event is a point in time and does not consume any time or resource and is represented by a circle.

• Path: This is a continuous chain of activities from the beginning to the end of the project.

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Terms related to Network AnalysisActivity-on-Arc (AOA) Network

• A branch reflects an activity of a project.• A node represents the beginning and end of activities,

referred to as events.• Branches in the network indicate precedence relationships.• When an activity is completed at a node, it has been

realized.

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Terms related to Network AnalysisConcurrent Activities

• Activities can occur at the same time (concurrently).• Network aids in planning and scheduling.• Time duration of activities shown on branches.

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Terms related to Network AnalysisDummy Activities

• A dummy activity shows a precedence relationship but reflects no passage of time.

• Two or more activities cannot share the same start and end nodes.

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Example..

• Draw the AON network for this project.• What is the Critical Path and Project Duration?

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Solution..

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Critical Path Method & Network Analysis