Project Management Ch11 Project Scheduling Critical Chain
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Transcript of Project Management Ch11 Project Scheduling Critical Chain
Chapter 11
Critical Chain Project Scheduling
11-01
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall
Chapter 11 Learning Objectives
After completing this chapter, students will be able to:
Understand the differences between common cause and special cause variation in organizations.
Recognize the three ways in which project teams inflate the amount of safety for all project tasks.
Understand the four ways in which additional project task safety can be wasted.
11-02
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall
Chapter 11 Learning Objectives
After completing this chapter, students will be able to:
Distinguish between critical path and critical chain project scheduling techniques.
Understand how critical chain methodology resolves project resource conflicts.
Apply critical chain project management to project priorities.
11-03
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall
Theory of Constraints & Critical Chain Project Scheduling
A constraint limits any system’s output.
The Goal – Goldratt
TOC Methodology
1. Identify the constraint
2. Exploit the constraint
3. Subordinate the system
4. Elevate the constraint
5. Repeat the process
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FIGURE 11.2 Five Key Steps in Theory of Constraint Methodology
11-05 Copyright © 2012 Pearson Education, Inc. Publishing as Prentice Hall
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall
Variation Common Cause
Inherent in the system
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Special Cause
Due to a special circumstance
Managers should
• Understand the difference between the two types
• Not adjust the process if variation is common cause
• Not include special cause variation in risk simulation
• Not aggregate discrete project risks
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall
CCPM and the Causes of Project Delay
How safety is added to project activities
1. Individual activities overestimated
2. Project manager safety margin
3. Anticipating expected cuts from management
11-07
time
25%
50%
80% 90%
Gaussian (lognormal)
Distribution
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall
Wasting Extra Safety Margin 1. The Student Syndrome
a. Immediate deadlines
b. Padded estimates
c. High demand
2. Failure to pass along positive variation a. Other tasks
b. Overestimation penalty
c. Perfectionism
3. Multitasking
4. Path Merging 11-08
FIGURE 11.6
Student Syndrome Model
11-9 Copyright © 2012 Pearson Education, Inc. Publishing as Prentice Hall
Effects of Multitasking on Activity Durations
11-10
FIGURE 11.7
Copyright © 2012 Pearson Education, Inc. Publishing as Prentice Hall
FIGURE 11.8
Effect of Merging Multiple Activity Paths
11-11 Copyright © 2012 Pearson Education, Inc. Publishing as Prentice Hall
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall
Critical Chain Solutions
Central Limit Theorem
Activity durations estimated at 50% level
Buffer reapplied at project level
– Goldratt rule of thumb (50%)
– Newbold formula
Feeder buffers for non-critical paths
11-12
n
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall
CCPM Changes Due dates & milestones eliminated
Realistic estimates – 50% level not 90%
“No blame” culture
Subcontractor deliveries & work scheduled ES
Non critical activities scheduled LS
Factor the effects of resource contention
Critical chain usually not the critical path
Solve resource conflicts with minimal disruption
11-13
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall
Critical Chain Solutions
11-14
Bob
Feeder
Buffer
Feeder
Buffer
Feeder
Buffer
Project
Buffer Bob
Bob
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall
Critical Chain Project Portfolios
Drum – system-wide constraint that sets the beat for the firm’s throughput
–company policy
–one person
–a department/work unit
–a resource
• Capacity constraint buffer – safety margin between projects
• Drum buffer – extra safety before the
constraint
11-15
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall
Applying CCPM to Project Portfolios
1. Identify the drum
2. Exploit the drum
a. Prepare a schedule for each project
b. Determine priority for the drum
c. Create the drum schedule
3. Subordinate the project schedules (next slide)
4. Elevate the capacity of the drum
5. Go back to step 2
11-16
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall
Subordinating Project Schedules
Schedule projects based on drum
Designate critical chain
Insert capacity constraint buffers
Resolve any conflicts
Insert drum buffers so the constraint is not starved
11-17
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall
CCPM Critiques
No milestones used
Not significantly different from PERT
Unproven at the portfolio level
Anecdotal support only
Incomplete solution
Overestimation of activity duration padding
Cultural changes unattainable 11-18
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall
Summary
Understand the differences between common cause and special cause variation in organizations.
Recognize the three ways in which project teams inflate the amount of safety for all project tasks.
Understand the four ways in which additional project task safety can be wasted.
Distinguish between critical path and critical chain project scheduling techniques.
Understand how critical chain methodology resolves project resource conflicts.
Apply critical chain project management to project priorities.
11-19
11-20 Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall