Content by Donald J. Wheeler

Donald J. Wheeler's picture
Donald J. Wheeler
Sometimes we use a chart for individual values and a moving range (an XmR chart) to assess the homogeneity of a finite data set. Since this is an "off-label" use for the XmR chart, we first...
Donald J. Wheeler's picture
Donald J. Wheeler
Last month I mentioned that we can put autocorrelated data on a process behavior chart. But what is autocorrelated data and what does it tell us about our processes? This article will use examples...
Donald J. Wheeler's picture
Donald J. Wheeler
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...
Donald J. Wheeler's picture
Donald J. Wheeler
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...
Donald J. Wheeler's picture
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...
Donald J. Wheeler's picture
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. What the F-ratio does The F-...
Donald J. Wheeler's picture
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...
Donald J. Wheeler's picture
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...
Donald J. Wheeler's picture
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...
Donald J. Wheeler's picture
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...