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Common Cause Variation is a type of variation which is natural and inherent to a process. Common Causes act randomly and independently of each other, are difficult to eliminate, and often require changes to a process or system.

The output of Common Cause variation generally conforms to a normal distribution and is stable over the time. Contrast this to Special Cause Variation, which often manifests as an outlier, shift, trend or some other signal on a graph and is therefore easier to identify and fix without significant modifications to a system.

For a better understanding of Common Cause Variation and an overview of Lean Six Sigma, check out our Free Lean Six Sigma Yellow Belt Training, Green Belt Training or Lean Training.

Elisabeth Swan

Elisabeth is a Master Black Belt at, the co-author of The Problem-Solver’s Toolkit and co-host of the Just-in-Time Cafe. For over 30 years, she's helped leading organizations like Amazon, Charles Schwab and Marriott International, Inc. build problem-solving muscles with Lean Six Sigma to achieve their goals.
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