Letting You In On a Little Secret

Cause I’m a nice guy, I’m going to give you articles that explain the basics of MSA.

Mon, 11/30/2009 - 05:00

You know how sometimes you think everyone knows a secret that they haven’t let you in on? Well, I had the opposite happen to me the other day. I assumed everyone knew the purpose for measurement system analysis (MSA), a.k.a. gauge repeatability and reproducibility; but I found out that a number of people have a completely mistaken impression of what they are for, much less how to do them correctly. So I thought I would give away, (free of charge) articles that explain the basics of MSA, as well as a cool MSA spreadsheet to help you learn how to do them, just because that’s the kind of guy I am. Selfless. And humble. Yep.

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OK, so it turns out that there is a lot going on in an MSA. I’m only going to cover the basics, but if you are willing to learn repeated measures analysis of variance (ANOVA), there are tons more you can do with data such as these. But there is a lot you can tell even with just statistical process control and some basic stats built into a spreadsheet.

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Comments

Thank you for discussing such an important topic. The article states, "So the end result of measurement system analysis is quantifying your ability to make the right decision about product conformance to specification."

Please note that there are other reasons for a MSA besides assessing the ability to use the system for Accept/Reject decisions. Often, the desire of a measurement is to provide an estimate of the value of some property. The research question guiding the MSA in these cases is to simply quantify the precision of the estimate of those measurements. And further, you may wish to understand the sources of variation in the measurement process.

Using a couple health care examples, let's assume you want to assess a system to measure LDL cholesterol or blood glucose. Your interest in using the measurements is not to determine if a person is "in-spec," but to somehow quantify the state of the person. And is so doing, you will want to ask yourself, "How good is this estimate?"

If we had an automatic control system, we might be interested in understanding the precision of the estimates of the input parameters.

In all these cases, a MSA gives us great insight.

Mike is absolutely correct that there are multiple reasons for performing an MSA. (Hi Mike! Mike is the programmer for the MVPstats stats software I use all the time.) I am just taking the most common example specifically for the article, but he is correct to point out there are a number of other reasons for quantifying your measurement error.

Thanks for dropping by, Mike, and for the comment!

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