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Control Charts are time charts designed to display signals or warnings of special cause variation. Special cause variation, as distinct from common cause variation, refers to changes in process performance due to sporadic or rare events indicating that a process is not “in control.” The advantage of Control Charts is that they enhance the understanding of process variation making it easier to take action to reduce special cause variation and improve ongoing process performance.

Graphically, they feature points that represent project mean or variation, and upper and lower Control Limits. The location of these points determines if a project is “out of control” and under the influence of common or special causes.

For a better understanding of the Control Chart 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 Managing Partner at, the co-author of The Problem-Solver’s Toolkit and co-host of the Just-in-Time Cafe. For over 25 years, she's helped leading organizations like Amazon, Charles Schwab and Starwood Hotels & Resorts build problem-solving muscles with Lean Six Sigma to achieve their goals.