Content by Donald J. Wheeler
A History of the Chart for Individual ValuesThe ultimate in homogeneous subgroups
Mon, 07/10/2017 - 12:03
The simplest type of process behavior chart is the chart for individual values and a moving range. It allows us to plot a point every time we get a value, making it perfect for data that occur one value at a time. A brief history of this simple…
We All Have to Use Less Than Perfect Data And process behavior charts work better than you know with imperfect data
Mon, 06/05/2017 - 12:03
In their recent article, “We Do Need Good Measurements,” Professors Stefan H. Steiner and R. Jock MacKay take exception to two of my Quality Digest articles, “Don’t We Need Good Measurements?” and “The Intraclass Correlation Coefficient.” While we…
More Capability ConfusionA little algebra, done correctly, can take you to places that don’t exist
Mon, 05/01/2017 - 12:03
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…
An F-Test for the 21st CenturyNo one wants to use 100-year-old techniques!
Mon, 04/03/2017 - 12:03
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. What the F-ratio does The F-ratio, created by Sir Ronald Fisher around 1925, is a…
The Three-Way ChartSome data structures need more than an average and range chart
Mon, 03/06/2017 - 12:03
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…
Don’t We Need Good Measurements? Process behavior charts work with imperfect data
Mon, 02/06/2017 - 11:03
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…
Evaluating Destructive MeasurementsYou can still put an upper bound on measurement error
Mon, 01/09/2017 - 12:01
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? All of the techniques for assessing the quality…
The Calibration of Measurement SystemsThe art of using a consistency chart
Mon, 12/05/2016 - 10:43
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?…
Election FraudIt’s not paranoia when they are stealing your votes
Wed, 11/23/2016 - 09:25
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…
How Do You Get the Most Out of Any Process?With a process behavior chart: the locomotive of continual improvement
Mon, 11/07/2016 - 11:41
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…