1. Critical Chain Project Scheduling
Chapter 11
Critical Chain Project Scheduling

2. 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.

3. 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.

4. Theory of Constraints & Critical Chain Project Scheduling
A constraint limits any system’s output.
The Goal – Goldratt
TOC Methodology
Identify the constraint
Exploit the constraint
Subordinate the system
Elevate the constraint
Repeat the process

5. FIGURE 11.2 Five Key Steps in Theory of Constraint Methodology
Copyright © 2012 Pearson Education, Inc. Publishing as Prentice Hall

6. Variation Special Cause Due to a special circumstance Managers should
Common Cause
Inherent in the system
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

7. CCPM and the Causes of Project Delay
How safety is added to project activities
Individual activities overestimated
Project manager safety margin
Anticipating expected cuts from management
time
25%
50%
80%
90%
Gaussian (lognormal) Distribution

8. Wasting Extra Safety Margin
The Student Syndrome
Immediate deadlines
Padded estimates
High demand
Failure to pass along positive variation
Other tasks
Overestimation penalty
Perfectionism
Multitasking
Path Merging

9. Student Syndrome Model
FIGURE 11.6  
Copyright © 2012 Pearson Education, Inc. Publishing as Prentice Hall

10. Effects of Multitasking on Activity Durations
FIGURE 11.7  
Copyright © 2012 Pearson Education, Inc. Publishing as Prentice Hall

11. Effect of Merging Multiple Activity Paths
FIGURE 11.8  
Copyright © 2012 Pearson Education, Inc. Publishing as Prentice Hall

12. 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

13. 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

14. Critical Chain Solutions
Bob
Feeder Buffer
ProjectBuffer
Buffers protect constraints and prevent delays

15. 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

16. Applying CCPM to Project Portfolios
Identify the drum
Exploit the drum
Prepare a schedule for each project
Determine priority for the drum
Create the drum schedule
Subordinate the project schedules (next slide)
Elevate the capacity of the drum
Go back to step 2

17. 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

18. 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

19. 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.

20. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall