Pugh method or decision-matrix method

This is a method for concept selection using a scoring matrix called the Pugh Matrix.  It is implemented by establishing an evaluation team, and setting up a matrix of evaluation criteria versus alternative embodiments.  This is the scoring matrix usually associated with the QFD method and is a form of prioritization matrix. Usually, the options are scored relative to criteria using a symbolic approach (one symbol for better than, another for neutral, and another for worse than baseline). These get converted into scores and combined in the matrix to yield scores for each option.

• Effective for comparing alternative concepts
• Scores concepts relative to one another
• Iterative evaluation method
• Most effective if each member of a design tean performs it independently and results are compared.

Comparison of the scores generated gives insight into the best alternatives.

Steps to Use/Construct Pugh matrix:

1.     Choose or develop the criteria for comparison. 

• Examine customer requirements to do this.

• Generate a set of engineering requirements and targets.

2.      Select the Alternatives to be compared.

        The alternatives are the different ideas developed during concept generation.  All concepts should be compared at the same level of generalization and in similar language.

3.      Generate Scores.

    Usually designers will have a favorite design, by the time it comes to pick one.  This concept can be used as datum, with all the other being compared to it as measured by each of the customer requirements.  If the problem is to redesign an existing product, then the existing product can be used as the datum.

    For each comparison the product should be evaluated as being better (+), the same (S), or worse (-).  Alternatively, if the matrix is developed with a spreadsheet like Excel, use +1, 0, and –1 for the ratings. 

If it is impossible to make a comparison, more information should be developed.

4.      Compute the total score

• Four scores will be generated, the number of plus scores, minus scores, the overall toal and the weighted total. 
• The overall total is the number of plus scores- the number of minus scores.
• The weighted total is the scores times their respective weighting factors, added up.

• The totals should not be treated as absolute in the decision making process but as guidance only.

• If the two top scores are very close or very similiar, then they should be examined more closely to make a more informed decision.

5.      Variations on scoring

    A number of variations on scoring Pugh’s method exist.  For example a seven level scale could be used for a finer scoring system where:

• +3  meets criterion extremely better than datum
• +2  meets criterion much better than datum
• +1  meets criterion better than datum
•   0  meets criterion as well as datum
• -1  meets criterion not as well as datum
• -2  meets criterion much worse then the datum
• -3  meets criterion far worse than the datum

General Format for a Pugh Matrix: