All Features
Donald J. Wheeler
In the past two months we have looked at how three-sigma limits work with skewed data. This column finds the power functions for the probability limits of phase two charts with skewed probability models, and compares the trade-offs made by three-sigma limits with the trade-offs made by the…
Jody Muelaner
One of the key ideas in lean manufacturing is that defects should be detected as early as possible. Efforts to control manufacturing processes, so that issues can be detected before defects occur, actually predate lean. Statistical process control (SPC) is a set of methods first created by Walter A…
Bill Snyder
In 1500, China’s economy was the strongest in the world. But by the 19th century, the United States, Western Europe, and Japan had leapfrogged over China by churning out goods and services in vast quantities while the former superpower stalled.
Why? Some economists argue that China’s lack of free…
Anthony D. Burns
You’ve set aside Sunday afternoon to bake some cookies, but you discover you have run out of eggs. Your partner in marital bliss has gone out and taken the car. You call a couple of mates, and they tell you to try bananas, vegetable oil, or applesauce as egg substitutes. You decide to have some fun…
Christopher Shoe
According to a recent LNS Research survey, 37 percent of quality leaders cite an inability to measure quality metrics as their No. 1 barrier to achieving quality goals. Even worse, the survey showed four in five companies have poor visibility into real-time metrics.
These figures highlight a…
Donald J. Wheeler
Last month I looked at how the fixed-width limits of a process behavior chart filter out virtually all of the routine variation regardless of the shape of the histogram. In this column I will look at how effectively these fixed-width limits detect signals of economic importance when skewed…
Yen Duong, Knowable Magazine
If you think it’s hard to tell how you’re doing at your job, imagine being a hockey goalie. Let’s say you block every shot in a game. Was that performance due to your superior skills? Or maybe just to a lack of skill in your opponents?
Evaluating ice hockey players' performance is getting easier,…
Donald J. Wheeler
The oldest myth about process behavior charts is the myth that they require “normally distributed data.” If you have ever heard this idea, or if you have ever taught this to others, then you need to read this article.
While this myth dates back to 1935, and while Walter Shewhart exposed this idea…
Steve Moore
Pickleball is arguably the fastest-growing sport in the United States, especially among baby-boomer retirees. This game is similar to tennis, but is played on a smaller court (44 ft × 20 ft) with a solid paddle and a perforated polymer ball much like a wiffle ball.
Pickleball’s popularity may be…
Davis Balestracci
As statistical methods become more embedded in everyday organizational quality improvement efforts, I find that a key concept is often woefully misunderstood, if it is even taught at all. W. Edwards Deming distinguished between two types of statistical study, which he called “enumerative” and “…
Jody Muelaner
In a general sense, capability is the ability to do something. Within manufacturing, capability is given a much more specific definition. It is an expression of the accuracy of a process or equipment, in proportion to the required accuracy.
This can be applied to production processes, in which…
Donald J. Wheeler
Recently I have had several questions about which bias correction factors to use when working with industrial data. Some books use one formula, other books use another, and the software may use a third formula. Which one is right? This article will help you find an answer.
Before we can…
Rohit Mathur
Whatever the process or type of data collected, all data display variation. This is also true in software development. Any measure or parameter of interest to our business will vary from time period to time period, e.g., number of incidents per week or month, time taken in resolving incidents,…
Donald J. Wheeler
During the past three months James Beagle and I presented columns that made extensive use of analysis of means techniques. Since these techniques may be new to some, this column explains when to use each technique and where to find tables of the appropriate scaling factors.
In 1967, Ellis R. Ott…
Romesh Saigal, Abdullah AlShelahi
Soon after the Great Recession, the U.S. stock markets plunged—and rebounded within 36 minutes. The Dow Jones Industrial Average dropped more than 9 percent, losing more than 1,000 points before suddenly recovering.
This May 6, 2010, event was the first recorded “flash crash.” Although it didn’t…
Scott A. Hindle
In everyday language, “in control” and “under control” are synonymous with “in specification.” Requirements have been met. Things are OK. No trouble.
“Out of control,” on the other hand, is synonymous with “out of specification.” Requirements have not been met. Things are not OK. Trouble.
Using…
Chad Kymal, Gregory F. Gruska
During the early 1980s, GM, Ford, and Chrysler established the Automotive Industry Action Group (AIAG), a not-for-profit organization with the mission “To improve its members’ competitiveness through a cooperative effort of North American vehicle manufacturers and their suppliers.” In the late…
Davis Balestracci
Recently, I’ve had a sad, increasing sense of déjà vu. Twitter has become even more vacuous, and LinkedIn has quickly devolved into a business version of Facebook. Literally right after I finished this draft, I read a newspaper headline: “Twitter Use Eroding Intelligence. Now there’s data to prove…
James Beagle III, Donald J. Wheeler
In Parts One and Two we defined the equivalence of instruments in terms of bias and measurement error based on studies using a single standard. Here we look at comparing instruments for differences in bias or differences in measurement error while using multiple standards.
When we use multiple…
Jay Arthur—The KnowWare Man
When I first learned quality improvement back in 1989 at Florida Power and Light, the consultants who trained us taught a very specific way to draw a Pareto chart. They’d been trained in Japan, the place where quality improvement first took root during the 1950s, so I took it for granted that the…
Ryan E. Day
Current business conversation often focuses on data and big data. Data are the raw information from which statistics are created and provide an interpretation and summary of data. Statistics make it possible to analyze real-world business problems and measure key performance indicators that enable…
William A. Levinson
Anthony Chirico1 describes how narrow-limit gauging (NLG, aka compressed limit plans) can reduce enormously the required sample size, and therefore the inspection cost, of a traditional attribute sampling plan. The procedure consists of moving acceptance limits t standard deviations inside the…
Adam Pintar
Now, if you’re familiar with either statistics or J.R.R. Tolkien, I know the title grabbed your attention. And if not, don’t worry; all will become clear in time, but I’ve always wanted to reference The Lord of the Rings in a title (and scientific papers provide little opportunity for that).…
Donald J. Wheeler, James Beagle III
Last month we provided an operational definition of when measurement systems are equivalent in terms of bias. Here we will look at comparing the within-instrument measurement error between two or more systems.
Once again we must emphasize that it makes no sense to seek to compare measurement…
Edwin Amenta
Ever since sportswriter Henry Chadwick popularized the box score in the 19th century, baseball fans have had a love affair with statistics. Many can recite records like Joe DiMaggio’s 56-game hitting streak, Rickey Henderson’s 130 stolen bases, or Barry Bonds’ 73 home runs in one season. But have…