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The Chi-Square Test is a hypothesis test that determines whether a statistically significant difference (aka variance) exists between two or more independent groups of discrete data, ruling out chance. It is useful for determining whether or not improvement implementations have been successful.

This test is performed on count data from different samples. An example would be: Assembly Line A produced 462 good parts and 265 defective parts whereas Assembly Line B produced 538 good parts and 321 defectives and you want to determine if Line A is truly better or the difference is just due to random chance.

For a better understanding of the Chi-Square Test 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 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.

Tracy O'Rourke

Tracy is a Managing Partner at She is also a Lean Six Sigma Green Belt Instructor at UC San Diego and teaches in San Diego State University’s Lean Enterprise Program. For almost 20 years, she has helped leading organizations like Washington State, Charles Schwab and GE build problem-solving muscles.