The Pugh Matrix

By Rob Thompson

The Pugh matrix was invented by Stuart Pugh at the University of Strathclyde in Glasgow, Scotland. It was designed as an approach for evaluating multiple options against each other, relative to a baseline option. It goes by many other names, here are just a few:

  1. Decision matrix/grid
  2. Selection matrix/grid
  3. Problem matrix
  4. Opportunity analysis
  5. Criteria rating form
  6. Criteria-based matrix

What do you do?

  1. Identify relevant user requirements, from say a QFD.
  2. Develop weights for each of the requirements.
  3. Generate several viable design concepts.
  4. Select one of the concepts as a baseline.
  5. Evaluate each concept against the datum for each of the criteria. Determine whether it is better (+), the same (S), or worse(-) than the baseline.
  6. For each column, determine the total number of pluses, minuses, and sames.
  7. Combine the best elements of each initial concept into a final optimal concept.

Example
pugh1.jpg
A new product is being designed and each desired concept was compared with the existing design. If the criteria is the same as in the existing design, a “S” is given, if it is better a “+” is given and if it is worse a “-” is given.  The sum of the sames, pluses, and minuses are consolidated. The “+”s indicate the strengths and the “-“s indicate the weaknesses.  A concept, which has more strength, is selected. In the example shown above (click picture to enlarge), concept 2, which has more strength, is selected.

How can it be applied in six sigma?

From sixsigmafirst:

  1. Define the problem.
  2. Define the cross-functional team that will work on the problem.
  3. Define what we consider to be the “baseline” e.g. a product or process that we have in place that is considered non-optimal.
  4. Define the requirements (CTQs ~“attributes”) and criteria that will be used in the analysis.
  5. Define the alternative concepts that will be included in the analysis.
  6. Define rating scale that will be used in the prioritization and trade-off attribute analysis.
  7. Define the scaling criteria that will be used in the concept analysis.
  8. Set up the Pugh Matrix.
  9. Analyze and rank each concepts benefit.
  10. Select the concept(s) that detail the most benefit.
  11. Initiate development/optimization analysis activities on the concept chosen.

Finally, iSixSigma has a great summary here:

A significant part of business success can come from the speed and quality of decision-making. Such good decision-making leads to performance improvements by reducing rework and driving benefits to the bottom line faster. Six Sigma, especially Design for Six Sigma (DFSS), has tools that improve the speed and quality of decisions. A morphological matrix will help identify potential solutions and define functional requirements for each solution. A Pugh matrix will help rank potential solutions against the voice of the customer (VOC).

Free Resources

Here is an example of a decision matrix and here is a free copy of a Grid Analysis Worksheet.

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