Measure
Measurement System Analysis – Attribute Data
In Article 19, we explored everything around Sampling. Now, let's delve into Measurement System Analysis and understand the Variation in the Measure Phase in this article.
Measurement System Analysis (MSA) is a key tool in Six Sigma to assess the accuracy and precision of your measurement process. It helps you identify and reduce the sources of variation that affect your data quality and process capability. These are the measurement attributes:
Accuracy – the disparity between the observed average measurement and a standard.
Repeatability – the variation observed when one person repeatedly measures the same unit with the same measuring equipment.
Reproducibility – the variation observed when two or more people measure the same unit with the same measuring equipment.
Stability – the variation obtained when the same person measures the same unit with the same equipment over an extended period of time.
Linearity – the consistency of accuracy across the entire range of the measurement system.
In order to assess the accuracy and precision of our measurement process, we need to gage the R&R, and its acceptable range.
Gage R&R (Repeatability and Reproducibility) is defined as the process used to evaluate a gauging instrument’s accuracy by ensuring its measurements are repeatable and reproducible. The process includes taking a series of measurements to certify that the output is the same value as the input and that the same measurements are obtained under the same operating conditions over a set duration.
For Attribute data, Gage R&R acceptable range is:
· 90% match for Repeatability, Reproducibility, and Accuracy analysis.
· Sample size should be 30-50 if possible.
Attribute Data MSA – Repeatability Test
In this test case, we have 120 Opportunities, 13 non-matches, and 107 matches. The Repeatability is calculated as Repeatability = 107/120 = 89.17%
Attribute Data MSA – Reproducibility Test
In this test case, we have 40 Opportunities, 19 non-matches, and 21 matches. The Reproducibility is calculated as Reproducibility = 21/40 = 52.5%
Attribute Data MSA – Accuracy Test
In this test case, we have 360 Opportunities, 40 non-matches, and 320 matches. The Accuracy is calculated as Accuracy = 320/360 = 88.89%
MSA Sources of Errors
Repeatability
· Operational definitions
· Maintain stability
Reproducibility
· Operational definitions
· Consistent use of gage
· Training
· Varying work environment
· Human/physical characteristics
· Performance measures
· Unclear requirements
Accuracy
· Instrument used improperly by appraiser
· Operational definition
· Standard not understood
Now that we've explored Measurement System Analysis for Attribute Data in the Measure Phase, I encourage you to continue our journey with us. Join us in the next article where we'll focus on Measurement System Analysis for Continuous Data and delve deeper into the Measure Phase.
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