What’s A Mann-Whitney Test?

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.

Learn more about Mann-Whitney Tests in Analyze Phase, Module 4.4.3 of Black Belt Training.

How To Run A Mann-Whitney Test In SigmaXL

Download the GoLeanSixSigma.com Mann-Whitney Test Data Set for SigmaXL here.

1. Select Raw Data:


2. Go to Statistical Tools > Non-Parametric Tests > 2 Sample Mann-Whitney:


3. Select Next:


4. Select Stacked Column Format

5. Highlight Total Order Lead Time and click the “Numeric Data Variable” once to enter the data into the tab.

6. Highlight Weekday vs. Weekend and click “Group Category” once to enter the data into the tab.

7. Click OK:


To learn more about Mann-Whitney Tests, register for Black Belt Training and review Analyze Phase, Module 4.4.3.