Content By Donald J. Wheeler

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By: Donald J. Wheeler

Here we take a serious look at some nonsensical ideas about capability ratios. Following a quick review of predictability and capability and a brief discussion of the traditional ways of characterizing capability and performance, we will consider the shortcomings of four bits of capability confusion found in some of today’s software.

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By: Donald J. Wheeler

A recent question from a statistician in Germany led me to the realization that the F-test of analysis of variance (ANOVA) fame is in serious need of an update.

Donald J. Wheeler’s picture

By: Donald J. Wheeler

The average and range chart handles most situations where the data can be logically organized into homogeneous subgroups. However, this chart breaks down when faced with a hierarchical data structure containing two or more levels of routine variation. For these situations I developed the three-way chart in 1982.

Donald J. Wheeler’s picture

By: Donald J. Wheeler

Good measurements are like apple pie and motherhood. Who could ever be against having good measurements? Since we all want good measurements, it sounds reasonable when people are told to check out the quality of their measurement system before putting their data on a process behavior chart. Fortunately, this is simply one more bit of advice that is completely unnecessary.

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By: Donald J. Wheeler

What can be done when a test is destructive? How do we characterize measurement error? How can we determine if a test method is adequate for a given product or application? How can we check for bias?

Donald J. Wheeler’s picture

By: Donald J. Wheeler

Who can be against apple pie, motherhood, or good measurements? This is why everyone stands up and salutes when we are told to maintain our measurement systems in good calibration. But what is good calibration? By what method will we achieve it? And how will we know when we have it?

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By: Donald J. Wheeler

Opinion

There was an election in Xanadu recently. One of the issues that was repeatedly brought up was the possibility of election fraud. So out west in the town of Hawtch-Hawtch, the people got some “Hawtch-Hawtch bee watchers” to go out and watch the polls.

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By: Donald J. Wheeler

Now we come to the sixth way to use a process behavior chart. Here we are going to look at how one group of workers used their average and range chart to improve their process. Their part had only one critical dimension, and this dimension had a standard deviation of only 15 microns. What kind of high-tech product might this be? Read on.

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By: Donald J. Wheeler

While we may tweak things in production, we rarely get permission to conduct formal experiments with an operating production line. Production’s job is to make product, whereas experiments are what they do in R&D. So how can we learn about an existing production process without rocking the boat? This is where input and outcome charts have a role to play.