Six Sigma DMAIC Process - Control Phase - What are Control Charts?

Control Chart is a graphical tool that helps determine if a process is “in control or not”. A control chart has three zones and is graphically represented as:


Six Sigma Control Chart Zones


Common Causes and Special Causes which result with Variations
Characteristics of Common Causes:
  • Present all the time
  • Have a small effect individually
  • Result in random variation
  • Effect can be tolerated
Characteristics of Special Causes:
  • Not always present
  • Come from outside influences
  • Typically have bigger influence than common causes
  • Effect we want to hear about

Six Sigma Common Causes and Special Causes




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