Monday, April 12, 2010

Six Sigma Tool of the Month-Attribute Agreement

How many times has this happened to you? You’re leading a six sigma project on a transactional process of some kind, something not directly tied to manufacturing or measurement of product quality. You get to the Gage R&R step in Measure and struggle to figure out how to satisfy the requirement for a Gage R&R statistic to interpret. If that’s ever happened to you, I have a solution to this problem for you..

First, let’s discuss briefly the “spirit” of the Gage R&R requirement. The reason we want to do a Gage Study boils down to confidence and good decision making. In Measure, we do a Gage Study of the data used to generate the Project Y or Critical To Quality (CTQ) measurement. Why? So we can be confident that, as we carry that data forward to capability analysis and Root Cause Analysis in the Analyze phase, we can trust the conclusions that we will draw and the results we will see. That’s it, confidence and good decision making.

How do we gain confidence whent he data is based on a person judging the quality of a characteristic rather than an objective instrument? One way that works very well is called Attribute Agreement. Attribute agreement assesses the results of decision making by people and produces some key statistics that tell us whether the results are due to random chance or if our judgment appears to be better (or worse) than random chance. Attribute agreement produces a result that can be interpreted in a similar fashion to a traditional Gage R&R and the detailed statstical analysis can give insight into areas in need of improvement, just as a traditional Gage R&R can.

Attribute agreement analysis is an effective method for delivering a statistical interpretation of a subjective judgement decision made by people, allowing fact based improvements to be identified, implemented and measured. Attribute agreement analysis allows those leading projects without continuous data to measure the quality of that data and boost confidence in the capability of the system, and decisions that are made to improve it. For a more in-depth discussion of Atrribute Agreement including a case study where it was used effectively, including details on how to interpret the results go to this article that I wrote.

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