From the course: Six Sigma Foundations
Measurement system analysis
- In the morning, when I step on a bathroom scale, I am X pounds. When I visit the 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 or 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 0 when there is no one standing on it, although the temptation is to offset it by negative two so that I feel better when I'm two pounds 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 a 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. Any problems are corrected, and a 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 discrete or categorical data, such as the classification of defects or complaints into reasons codes. You need to perform a measurement system analysis to ensure that data is valid before they can be used. Otherwise, your project will be sidetracked, 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.
Download courses and learn on the go
Watch courses on your mobile device without an internet connection. Download courses using your iOS or Android LinkedIn Learning app.