The member will learn about the importance of doing a measurement system analysis to ensure valid data
- In the morning when I step on a bathroom scale, I am x pounds. When I visit a doctor's office that same day, the nurse weighs me and I end up at more than x pounds, which weight is correct? So which weighing scale should I use as I train for the Olympics? In this movie I will discuss the importance of ensuring that data is valid before using it. In Six Sigma projects, this is done using a technique called Measurement System Analysis, or MSA for short. MSA is done early during the measure phase so that any data to be collected and used is valid.
The Measurement System includes the entire system including the measuring instrument, the operator, and the procedures used to collect, measure, and record data. To be valid, measurements should be accurate with no bias, repeatable, and reproducible. Let's go back to my weight example. To be accurate with no bias, the bathroom scale should be centered on zero when there is no one standing on it, although the temptation is to offset it by negative two so that I feel better that I'm two pound lighter.
In other words, the equipment should be calibrated. To be repeatable means that if I weigh myself twice, or even three times on the same scale, I should get the same readings. The measurement is said to be repeatable. To be reproducible means that my weight at home should be the same as my weight in the doctor's office. If that is the case, the measurement is reproducible. However, in my case, my weight measured by the nurse is not the same as my weight at home so the measurement was not reproducible.
When the measurement system analysis, or MSA, is carried out, 20 to 25 known items are selected and in a blind study, each item is measured twice by at least two operators. Any inaccuracy, repeatability or reproducibility problems with the measurement system can be determined. And if problems are corrected, and the follow up MSA is carried out, to verify that the measurement system is good, and data collected is valid. MSA has to be done before any data is collected or used.
MSA is applicable to both types of data, it is applicable for continuous data such as weight or transaction time, and it is also applicable to discreet or categorical data such as the classification of defects or complaints into reason codes. You need to perform a measurement system analysis to ensure that data is valid before it can be used, otherwise, your project will be side tracked chasing the wrong problem, analyzing incorrectly, or drawing the wrong conclusions.
You definitely do not want to be a victim of invalid data. As the old saying goes, garbage in garbage out.
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- What is Six Sigma?
- Understanding key concepts such as Y = f(x) and sigma level
- Selecting Six Sigma projects and team members
- Planning in the Define phase
- Gathering data in the Measure phase
- Analyzing data in the Analyze phase
- Selecting and evaluating solutions in the Improve phase
- Developing a control plan in the Control phase