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.

Wed, 10/16/2024 - 12:03
Don’t Just Stand There, Improve Something!Working on the wrong things can make things worse
Wed, 08/21/2024 - 12:03
The objective of all improvement projects should be to improve the overall process. Everything else should be secondary to this objective. If you improve the efficiency of a support process, or even a portion of the core process, but at the same…
Third-Generation Capability ConfusionHow to make sure no one understands you
Wed, 07/03/2024 - 12:03
The four common capability and performance indexes collectively contain all of the summary information about process predictability, process conformity, and process aim that can be expressed numerically. As a result, any additional capability…
A History of the Chart for Individual ValuesThe ultimate in homogeneous subgroups
Wed, 06/12/2024 - 12:03
In May 1924, Walter Shewhart wrote a memo that contained the first example of a process behavior chart (i.e., a “control chart”). It was a chart for individual values that would be known today as a p-chart. Shewhart’s insight was that “three-sigma”…
One Technique, Many UsesThe versatility of Shewhart’s charts
Mon, 05/06/2024 - 12:03
One hundred years ago this month, Walter Shewhart wrote a memo that contained the first process behavior chart. In recognition of this centennial, this column reviews four different applications of the techniques that grew out of that memo. The…
The Test to Use Before All Other TestsHow to avoid mistakes in your analysis

Wed, 04/03/2024 - 12:03
When presented with a collection of data from operations or production, many will start their analysis by computing descriptive statistics and fitting a probability model to the data. But before you do this, there’s an easy test that you need to…
What You Need to Know About Weibull DistributionsThe more you know, the easier it becomes to use your data
Wed, 03/06/2024 - 12:03
Over the past two months we’ve considered the properties of lognormal and gamma probability models. Both of these families contain the normal distribution as a limit. To complete our survey of widely used probability models, this column will look at…
What You Need to Know About Gamma Probability ModelsThe more you know, the easier it becomes to use your data
Wed, 02/07/2024 - 12:03
Clear thinking and simplicity of analysis require concise, clear, and correct notions about probability models and how to use them. Here, we’ll examine the basic properties of the family of gamma and chi-square distributions that play major roles in…
What You Need to Know About Lognormal ModelsHow you can filter out noise
Mon, 01/08/2024 - 12:03
When do we need to fit a lognormal distribution to our skewed histograms? This article considers the basic properties of the lognormal family of distributions and reveals some interesting and time-saving characteristics that are useful when…
The Leptokurtophobia PandemicWhat are the symptoms?
Mon, 12/04/2023 - 12:03
Fourteen years ago, I published “Do You Have Leptokurtophobia?” Based on the reaction to that column, the message was needed. In this column, I would like to explain the symptoms of leptokurtophobia and the cure for this pandemic affliction.…
Can We Adjust Our Way to Quality?Part 2: By trying to do better, we can make things worse
Mon, 10/30/2023 - 12:03
In last month’s column, we looked at how process-hyphen-control algorithms work with a process that is subject to occasional upsets. This column will consider how they work with a well-behaved process. Last month we saw that process adjustments can…