Shows the relationship between two, three or four groups of information. It also can give information about the relationship, such as its strength, the roles played by various individuals or measurements. Six differently shaped matrices are possible: L, T, Y, X, C and roof-shaped, depending on how many groups must be compared.
Excerpted from Nancy R. Tague’s The Quality Toolbox, Second Edition, ASQ Quality Press, 2004, pages 338-344.
ASQ's Toolbox - Matrix Diagram - http://www.asq.org/learn-about-quality/new-management-planning-tools/overview/matrix-diagram.html