Special Cause

Understanding Common Cause vs. Special Cause Variation: Lessons from the Red Bead Experiment

For professionals in quality management and continuous improvement, the distinction between common cause and special cause variation forms the bedrock of effective process analysis and improvement. These concepts, famously demonstrated through Dr. W. Edwards Deming’s Red Bead Experiment, are essential for anyone committed to elevating organizational quality and empowering teams to make data-driven decisions. In this post, we’ll unpack the statistical definition of common and special cause variation, reveal why misunderstanding these concepts can lead to flawed management decisions, and explore practical takeaways using vivid examples inspired by the Red Bead Experiment.