© 2004 Cayman Business Systems
Rev: Pre-G3 - Rendered  Thursday, February 12, 2004
Slide 59
Elsmar.com  --- The Cove!
8-Disciplines Problem Solving
Elsmar.com
Establishing A Team (Flow)
Select
Champion
1. Recognition of Common Cause vs. Special
Cause Relationship
2. Common Policy / Goal But
Different Measures At Different Organizational
Levels
Select Team Members
Select Leader
Verify Cross-Functional Team
Representation & Expertise
Begin Investigation
Common causes are the myriad of ever-present factors (e.g., process inputs or conditions) that contribute in varying degrees to relatively small, apparently random shifts in outcomes day after day, week after week, month after month. The collective effect of all common causes is often referred to as system variation because it defines the amount of variation inherent in the system.

Special causes are factors that sporadically induce variation over and above that inherent in the system. Frequently, special cause variation appears as an extreme point or some specific, identifiable pattern in data. Special causes are often referred to as assignable causes because the variation they produce can be tracked down and assigned to an identifiable source. (In contrast, it is usually difficult, if not impossible, to link common cause variation to any particular source.) Special Cause variation results from events which are occurring outside the process. For example, a relatively major change in temperature or humidity could cause significant variation (points outside control limits) in the process.