The Test for Two Variances is a hypothesis test that determines whether a statistically significant difference exists between the variance of two independent sets of 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 Assembly Line A has product weights with a variance of 1 pound whereas Assembly Line B has product weights with a variance of 2 pounds and you want to determine if Line A truly has less variation or the difference is just due to random chance.

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Elisabeth Swan

Elisabeth is a Managing Partner & Executive Advisor at GoLeanSixSigma.com. 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 & Executive Advisor at GoLeanSixSigma.com. For almost 20 years, she's helped leading organizations like Washington State, Cisco and GE build problem-solving muscles with Lean Six Sigma to achieve their goals.