Content by Donald J. Wheeler

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Donald J. Wheeler
The Levey-Jennings chart was created in the 1950s to answer questions about the quality and consistency of measurement systems in the chemical and process industries. This column will illustrate...
Donald J. Wheeler's picture
Donald J. Wheeler
One computation that modern software offers to unsuspecting users is the statistical tolerance interval. Since this sounds very much like limits for individual values, some have been tempted to use...
Donald J. Wheeler's picture
Donald J. Wheeler
When industrial classes in statistical techniques began to be taught by those without degrees in statistics it was inevitable that misunderstandings would abound and mythologies would proliferate....
Donald J. Wheeler's picture
Donald J. Wheeler
In theory, there is no difference between theory and practice. In practice, there is. During the past three months we have looked at three families of probability models and found that they...
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Donald J. Wheeler
The best analysis is the simplest analysis that provides the needed insight. Of course this requires enough knowledge to strike a balance between the needed simplicity and unnecessary complexity....
Donald J. Wheeler's picture
Donald J. Wheeler
Story update 9/8/2015: There was an error in the data set for columns "Skew" and "Kurt" in figure 7. The error has been corrected. Clear thinking and simplicity of analysis...
Donald J. Wheeler's picture
Donald J. Wheeler
Some commonly held ideas about skewed probability models are incorrect. These incorrect ideas are one source of complexity and confusion regarding the analysis of data. By examining the basic...
Donald J. Wheeler's picture
Donald J. Wheeler
While the computations for a process behavior chart are completely general and very robust, the secret to using a process behavior chart effectively lies in the art of rational sampling and...
Donald J. Wheeler's picture
Donald J. Wheeler
While the computations for a process behavior chart are completely general and very robust, the secret to using a process behavior chart effectively lies in the art of rational sampling and rational...
Donald J. Wheeler's picture
Donald J. Wheeler
Parts per million (ppm) is part of the language of Six Sigma. It pervades the sales pitch and is used in all sorts of computations as a measure of quality. Yet what are the rules of arithmetic and...