The Matrix Diagram in Six Sigma is used to show the relationship between the various items in two or more groups. You can also show the strength or intensity of each relationship. This Six Sigma diagram helps you to recognize connections between disparate groups. Displaying all existing relationships in a graphical method will help you to make informed decisions.
An excellent source of additional information on this Six Sigma tool is Six Sigma Demystified by Paul Keller (McGraw-Hill, 2011).