BACK TO BASICS
Easier prioritization through cause and effect matrix
By Scott Force
Because quality professionals can’t address every customer complaint, eliminate all process defects or implement every solution a team develops, prioritization is vital. It keeps an organization focused on fixing its most significant issues and implementing solutions that yield the greatest impact.
As a certified quality engineer, I learned many techniques for process improvement, but it wasn’t until I received my lean Six Sigma Black Belt training that I discovered the cause and effect matrix—a tool I’ve used extensively in prioritizing items.
As part of the quality function deployment (QFD) house of quality, the cause and effect matrix allows you to rate or compare various items through a list of attributes with defined ranges for scoring. Table 1 shows an example of a cause and effect matrix used for comparing interview candidates based on three attributes: years of lean Six Sigma experience, salary requirements and number of completed projects.
The two key characteristics of the matrix are the weight of importance and the scoring criteria for attributes on a scale of zero, one, three or nine. When QFD was developed, its facilitators wanted to create a greater contrast between strong attributes (score of nine) and weaker ones (scores of zero, one or three). In the interview example (see Table 1), the scoring style allows candidates who scored nine in one or more attributes to have more influence on the final prioritization of future interviews.1
The math behind the scoring is simple: Each attribute’s weight of importance is multiplied by the customer’s rating of that attribute. These scores are added across the horizontal row and provide the final score.2 Table 1 shows candidates A, B and D meet more of the preferred attributes for the position and warrant follow-up communications or reference checks to determine how to proceed with future interviews.
In the context of lean Six Sigma projects, the cause and effect matrix narrows the list of process inputs and how they relate to process outputs. This helps teams investigate several things: how they should proceed through the measure phase of the define, measure, analyze, improve and control (DMAIC) process; the best prioritization of improvements to pilot in the improve phase; and how the matrix can be used as a strategy planning tool, comparing processes across an organization to decide where improvement efforts should be focused.
The cause and effect matrix allows for a methodical, disciplined approach to process improvement that’s similar to other methods, such as plan-do-check-act cycles and DMAIC. This is what’s always impressed me about process improvement: While I may not know the solutions to the problems my teams are assigned, I know that by following my training and trusting my tools, I always have a high probability of success.
- Louis Cohen, Quality Function Deployment: How to Make QFD Work for You, Prentice Hall, 1995, p. 144.
- Scott Force, "Creative Combination," Quality Progress, March 2012, p. 72.
Scott Force is an ASQ-certified quality technician, engineer and Six Sigma Black Belt. He earned a bachelor’s degree in manufacturing engineering from Miami University in Oxford, OH A senior member of ASQ, Force also is a Six Sigma Master Black Belt trained by Sigma Breakthrough Technologies Inc.