Statistical Tolerance IntervalsHow to make exact predictions
Mon, 01/04/2016 - 15:35
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 them on process behavior charts in place of the… The Secret Foundation of Statistical InferenceWhat you don’t know can hurt you
Tue, 12/01/2015 - 15:14
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. One of the things lost along the way was the secret… Shewhart and the Probability ApproachThe difference is much greater than how we compute the limits
Mon, 11/02/2015 - 14:39
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 share some remarkable properties. These properties provide… Properties of Probability Models, Part 3 What they forgot to tell you about the lognormals
Mon, 10/05/2015 - 16:43
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. In parts one and two of this series we looked at the… Properties of Probability Models, Part 2What they forgot to tell you about the Gammas
Tue, 09/01/2015 - 15:53
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 require concise, clear, and correct notions about probability models and… Properties of Probability Models, Part 1What they forgot to tell you about Weibull distributions
Mon, 08/03/2015 - 17:04
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 properties of skewed distributions this article can help… Rational Sampling More about the conceptual foundation of process behavior charts
Wed, 07/01/2015 - 17:03
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 subgrouping. Rational subgrouping was the topic… Rational SubgroupingThe conceptual foundation of process behavior charts
Mon, 06/01/2015 - 01:00
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 subgrouping. Rational subgrouping has to do with… The Parts-Per-Million ProblemWhen does a computation result in a number?
Mon, 05/11/2015 - 10:56
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 statistics that govern the computation and usage of… Numerical JabberwockyNumbers that gyre and gymble in the wabe
Wed, 04/01/2015 - 16:40
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 gives a couple of the more egregious examples I have…
