All Features
Eston Martz
Whatever industry you’re in, you’re going to need to buy supplies. If you’re a printer, you’ll need to purchase inks, various types of printing equipment, and paper. If you’re in manufacturing, you’ll need to obtain parts that you don’t make yourself. But how do you know you’re making the right…
Scott A. Hindle
When considering how good a production process is, it’s important to ask, “Can we expect the output to be fully conforming?” An assessment of process capability can answer this. Data are needed, but how many? Is “30” the right number? This article examines these last two questions.
First, why 30…
Douglas Allen
It’s a cold winter’s night in northern New Hampshire. You go out to the woodshed to grab a couple more logs, but as you approach, your hear a rustling inside the shed. You’ve gotten close enough to know you have a critter in the woodpile. You run back inside, bolt the door, hunker down with your .…
Donald J. Wheeler
Story update 9/8/2015: There was an error in the data set for columns "Skew" and "Kurt" in figure 7. The error has been corrected.
Clear thinking and simplicity of analysis require concise, clear, and correct notions about probability models and how to use them. Last month in part one we looked…
Joel Smith
Just 100 years ago, very few statistical tools were available and the field was largely unknown. Since then, there has been an explosion in available tools, as well as ever-increasing awareness and use of statistics.
Although most readers of this column are looking to pick up new tools or improve…
John Flaig
I have discussed the economics of project management numerous times in presentations all over the country, and based on the response to my message, I have to conclude that many people just don’t get it.
Let me again sound the wake-up call with a quote from V. S. Liebhold, co-author of the article…
Donald J. Wheeler
Some commonly held ideas about skewed probability models are incorrect. These incorrect ideas are one source of complexity and confusion regarding the analysis of data. By examining the basic properties of skewed distributions this article can help you to greater clarity of thought and may even…
Joel Smith
Last month, the ESPN series Outside the Lines reported on baseball pitchers suffering serious injuries from being struck in the head by line drives, and the efforts that Major League Baseball (MLB) is making toward having protective gear developed for pitchers.
You can view the report here if you…
Davis Balestracci
This is a continuation of my last column, which I’ve written to honor my late dad who loved golf. As promised, let’s look at the Masters golf tournament final four-round scores for the 55 players who survived the cut. We’ll analyze and then give it a twist based on the ongoing enumerative vs.…
Donald J. Wheeler
While the computations for a process behavior chart are completely general and very robust, the secret to using a process behavior chart effectively lies in the art of rational sampling and rational subgrouping. Rational subgrouping was the topic of last month’s column. Here we shall look at the…
John Flaig
The classic version of FMEA is an engineering tool for quality and reliability improvement through project prioritization. It was formally released by the U.S. government with MIL-P-1629 in 1949 and updated in 1980 as MIL-STD-1629A. The classic FMEA methodology has proven to be reasonably…
Davis Balestracci
To celebrate Father’s Day in the United States (June 21 this year), I’m going to use this and my next column to honor my late dad by using a game he loved—golf—to teach some very basic statistics lessons. Some of these may have been lost on you previously, not through some fault of your own, but…
Patrick Runkel
I’ve never understood the fascination with selfies.
Maybe it’s because I'm over 50. After surviving the slings and arrows of a half a century on Earth, the minute or two I spend in front of the bathroom mirror each morning is more than enough selfie time for me.
Still, when I heard that Microsoft…
Patrick Runkel
It’s usually not a good idea to rely solely on a single statistic to draw conclusions about your process. Do that, and you could fall into the clutches of the “duck-rabbit” illusion shown below.
If you fix your eyes solely on the duck, you’ll miss the rabbit—and vice-versa.
If you’re using…
Donald J. Wheeler
While the computations for a process behavior chart are completely general and very robust, the secret to using a process behavior chart effectively lies in the art of rational sampling and rational subgrouping. Rational subgrouping has to do with organizing your data so that the chart will answer…
Dawn Keller
Generally speaking, I have a problem with authority. I don’t like being told what to do or how to do it. I’m not proud of that.
I recall debating with my high school trigonometry teacher regarding the value of the homework “process”—specifically in those situations where the student in question…
Donald J. Wheeler
Parts per million (ppm) is part of the language of Six Sigma. It pervades the sales pitch and is used in all sorts of computations as a measure of quality. Yet what are the rules of arithmetic and statistics that govern the computation and usage of parts per million? To discover the answers read…
Donald J. Wheeler
The first axiom of data analysis is: “No data have meaning apart from their context.” Yet we all encounter measures that have been dreamed up without regard for either context or use. This column gives a couple of the more egregious examples I have encountered over the years.
Kentucky Higher…
Patrick Runkel
Right now I’m enjoying my daily dose of morning joe. As the steam rises off the cup, the dark, rich liquid triggers a powerful enzyme cascade that jump-starts my brain and central nervous system, delivering potent glints of perspicacity into the dark crevices of my still-dormant consciousness.…
CorDEX Instruments
NFPA 70E, full title “NFPA 70E—“Standard for Electrical Safety in the Workplace,” is a standard written by the National Fire Protection Association (NFPA). NFPA 70E was created primarily to assist companies and their personnel in avoiding potential fatalities and injuries from electrocution, arc-…
Dawn Keller
Juvenile idiopathic scoliosis. That was the diagnosis given to my then 8-year-old daughter last January. In short, it means that she’s young (under 10), she exhibits an abnormal amount of spinal curvature, and there’s no identified cause (aside from some bad luck).
Emilia’s X-rays indicated an S-…
Donald J. Wheeler
Author clarification--3/5/2015:It appears that I somewhat overstated my case in this article. I had forgotten that there are some families of distributions where we can estimate the shape of a probability model using the statistics for location and/or dispersion. Because of this, these families get…
Joel Smith
I typically attend a few lean Six Sigma conferences each year, and at each there’s at least one session about compensating belts. There are any number of ideas for how to do so, but they commonly include systems that provide a percentage of savings as a portion of pay, or provide a bonus for…
Patrick Runkel
If you’re not a statistician, looking through statistical output can sometimes make you feel a like you’ve wandered into Alice in Wonderland. Suddenly, you find yourself in a fantastical world where strange and mysterious phantasms appear out of nowhere. For example, consider the T and P in your t…
Donald J. Wheeler
Whenever the original data pile up against a barrier or a boundary value, the histogram tends to be skewed and non-normal in shape. Last month in part one we found that this doesn’t appreciably affect the performance of process behavior charts for location. This month we look at how skewed data…