A typical use of the Matrix Diagram to compare two lists is where the list on the left represents a problem (the 'what') and the list above represents a solution to that problem (the 'how'). For example, the first list details customer requirements for a product, whilst the second list shows how this is translated into design specifications. The relationship values now can be used to identify specific problems and other points of interest, for example:
Rows with low totals indicate customer requirements which are not well met.
Columns with low totals may indicate over-engineered or unnecessary design items.
Columns with high totals indicate design items which are particularly important for meeting a number of customer requirements.
A constraint when using a Matrix Diagram is in the number of comparisons that may practically be made. A ten-by-ten matrix requires 100 comparisons, which needs a moderate effort to complete. However, a complex product might have hundreds of requirement details and a corresponding number of design specification elements, but a hundred-by-hundred matrix needs a prohibitive 10,000 comparisons to be made!
A practical use of the Matrix Diagram in a complex situation, is for focusing on the detail of critical, suspect or difficult parts of the problem, rather than trying to use it for the entire situation.