Dr. Wheeler
Donald J. Wheeler

Author

SPC Press

Dr. Wheeler is a fellow of both the American Statistical Association and the American Society for Quality who has taught more than 1,000 seminars in 17 countries on six continents. He welcomes your questions; you can contact him at djwheeler@spcpress.com.

Mon, 12/08/2025 - 12:03
How Measurement Error Affects the Four Ways We Use Data Understanding probable error and the intraclass correlation coefficient makes it possible to quantify measurement uncertainty
Mon, 04/04/2011 - 05:30
Measurement error is generally considered to be a bad thing, and yet there is very little written about how measurement error affects the way we use our measurements. This column will consider these effects for four different uses of data. But first…
Three Questions for Success The necessity of using operational definitions
Tue, 03/01/2011 - 04:30
All improvement efforts require a framework. No matter what we are doing, we all need some way to align our efforts and focus on a specific objective. During my 40 years in this business, I have seen many different models offered as frameworks for…
A Better Way to Do R&R Studies Evaluating the measurement process approach
Tue, 02/01/2011 - 07:04
Last month’s column looked at how to fix some of the Problems with Gauge R&R Studies. This month I will show you how to learn more from your gauge repeatability and reproducibility (R&R) data with less effort. Rather than getting lost in a…
Problems With Gauge R&R Studies How to make sense of your repeatability and reproducibility (R&R) values
Mon, 01/03/2011 - 04:30
Measurement error is ubiquitous. As a result, over the past 250 years, different areas of science and engineering have come up with many different ways to deal with the problem. One approach to the problem of measurement error was developed during…
The Intraclass Correlation Coefficient Is your measurement system adequate?
Thu, 12/02/2010 - 15:26
In my July column, “Where Do Manufacturing Specifications Come From?” we found that the intraclass correlation coefficient is the natural measure of relative utility. This measure is theoretically sound and easy to explain. This column will look at…
Are You Sure We Don’t Need Normally Distributed Data? More about the misuses of probability theory
Mon, 11/01/2010 - 06:00
Last year I discussed the problems of transforming data prior to analysis (see my August 2009 column, “Do You Have Leptokurtophobia?,” my September 2009 column, “Transforming the Data Can Be Fatal to Your Analysis,” and my October 2009 column,“…
What Is the Zone of Economic Production? And how can you get there?
Mon, 10/04/2010 - 05:30
In my August column, “How to Turn Capability Indexes Into Dollars,” and my September column, “The Gaps Between Performance and Potential,” I showed how to convert capability indexes into the effective cost of production and use (ECP&U), and how…
The Gaps Between Performance and Potential Using the effective costs of production and use
Wed, 09/01/2010 - 06:00
In my August column, “How to Turn Capability Indexes Into Dollars,” I defined the effective cost of production and use and showed how it can be obtained directly from the capability and performance indexes. In this column, I will show how these…
How to Turn Capability Indexes Into Dollars The effective cost of production and use

Fri, 07/30/2010 - 08:03
Capability indexes allow us to characterize the relationship between the process potential and the specifications. Performance indexes characterize the past performance relative to the specifications. Yet, in practice, we seek to make sense of…
Where Do Manufacturing Specifications Come From? Standard deviation of conditional distribution of X given Y is the reason all measurement studies are built upon repeated measurements.
Tue, 07/06/2010 - 08:40
Evidently Steven Ouellette did not like my June column, “Is the Part in Spec?” The adjectives he used were “complicated,” “unhelpful,” “backward,” “confusing,” “unnecessary,” “crazy,” and “disastrous.” (Ouellette’s response, “Know the Process…