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The Mann-Whitney Test is a hypothesis test that determines whether a statistically significant difference exists between the medians of two independent sets of non-normally distributed continuous data. It is useful for determining if a particular strata or group could provide insight into the root cause of process issues.

An example would be if Pizza Delivery Person A has median delivery time of 15 minutes whereas Pizza Delivery Person B has median delivery time of 17 minutes and you want to determine if Person B is truly slower or if the difference is just due to random chance.

For a better understanding of the Mann-Whitney Test, check out our Black Belt Training & Certification Course!

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.