Statistics Features

John Niggl's picture
John Niggl
Ever wondered why quality control (QC) professionals check a sample instead of 100 percent of a shipment during inspection? Or maybe you’ve wondered why they use acceptance sampling, rather than...
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...
Davis Balestracci's picture
Davis Balestracci
Recently I demonstrated a common incorrect technique for comparing percentage rate performances—based of course in the usual normal distribution nonsense. Let’s revisit those data with a superior...
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...
Steve Daum's picture
Steve Daum
I have daily conversations with manufacturer plant managers, quality managers, engineers, supervisors, and plant production workers about challenges when using statistical process control (SPC). Of...
Davis Balestracci's picture
Davis Balestracci
My last column mentioned how doctors and hospitals are currently being victimized with draconian reactions to rankings, either interpreted literally or filtered through the results of some type of...
Derek Benson's picture
Derek Benson
How early is too early to introduce quality into your everyday life? Have we missed out on improvement opportunities in our personal lives along our paths to achieving our career goals as quality...
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...
Stefan H. Steiner's picture
Stefan H. Steiner
In his February 2017 Quality Digest column, “Don’t We Need Good Measurements?” Donald J. Wheeler recommends that a measurement system contributing up to 80 percent of the overall variation (on the...
Joel Smith's picture
Joel Smith
In parts one and two of “Gauging Gage,” we looked at the numbers of parts, operators, and replicates used in a gage repeatability and reproducibility (GR&R) study and how accurately we could...
Joel Smith's picture
Joel Smith
In part one of “Gauging Gage,” I looked at how adequate a sampling of 10 parts is for a gage repeatability and reproducibility (GR&R) study and provided some advice based on the results. Now...
Davis Balestracci's picture
Davis Balestracci
Don’t tell me you’re not tempted to look when you spot a magazine cover saying, “How does your state rank in [trendy topic du jour]?” Many of these alleged analyses rank groups on several factors,...
Joel Smith's picture
Joel Smith
‘You take 10 parts and have three operators measure each two times.” This standard approach to a gage repeatability and reproducibility (GR&R) experiment is so common, so accepted, so...
Fred Faltin's picture
Fred Faltin
All of us draw conclusions based on what we see happening around us. Often what we’re observing is a sample from some larger population of events, and we draw inferences based on the sample without...
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...
Steve Moore's picture
Steve Moore
When I entered college in the fall of 1970, I had a nice slide rule (or “slipstick” as some of us called it) that I proudly carried in a leather case to my engineering and chemistry classes....
Davis Balestracci's picture
Davis Balestracci
Many talk about reducing variation to improve quality. Does that include human variation, where everyone takes a different approach to improving overall improvement processes? What would...
Quality Transformation With David Schwinn's picture
Quality Transformation With David Schwinn
This month’s column comes from a convergence of finishing my article, “Statistical Thinking for OD Professionals,” for the OD Practitioner, and reading “How Statistics Lost their Power—and Why We...
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-...
Patrick Runkel's picture
Patrick Runkel
Did you ever wonder why statistical analyses and concepts often have such weird, cryptic names? One conspiracy theory points to the workings of a secret committee called the ICSSNN. The...