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
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...
Donald J. Wheeler
The first axiom of data analysis is: “No data have meaning apart from their context.” Yet we all encounter measures that have been dreamed up without regard for either context or use. This column...
Donald J. Wheeler
Author clarification--3/5/2015:It appears that I somewhat overstated my case in this article. I had forgotten that there are some families of distributions where we can estimate the shape of a...
Donald J. Wheeler
Whenever the original data pile up against a barrier or a boundary value, the histogram tends to be skewed and non-normal in shape. Last month in part one we found that this doesn’t appreciably...
Donald J. Wheeler
Whenever the original data pile up against a barrier or a boundary value, the histogram tends to be skewed and non-normal in shape. In 1967 Irving W. Burr computed the appropriate bias correction...
Donald J. Wheeler
Comparisons are often required as part of doing business. Are these two machines the same? Is this process the same as that process? Are two operators performing in the same way? In this article we...
Donald J. Wheeler
There is no virtue in obedience when we do not have a choice. But when we have a choice it helps to understand both the law and the reason behind the law. This column is about bad choices that are...
Donald J. Wheeler
Much of modern statistics is concerned with creating models which contain parameters that need to be estimated. In many cases these estimates can be severely affected by unusual or extreme...
Donald J. Wheeler
Outlier tests such as the W-ratio test and Dixon’s outlier test suffer from a problem that can mislead the user. This article will outline the problem and provide guidelines for the...
