All Features
Fred Schenkelberg
The planning of environmental or reliability testing becomes a question of sample size at some point. It’s probably the most common question I hear as a reliability engineer: How many samples do we need?
Also, when evaluating supplier-run test results, we need to understand the implications of…
Davis Balestracci
“It is impossible to tell how widespread data torturing is. Like other forms of torture, it leaves no incriminating marks when done skillfully. And like other forms of torture, it may be difficult to prove even when there is incriminating evidence.” —J. L. Mills
When will academics, Six Sigma…
William A. Levinson
The Shewhart control chart is relatively insensitive to non-normal distributions, and the worst foreseeable consequences of a wrong decision involve searching for an assignable or special cause when none is present. The economic consequences depend on the time wasted, and whether unnecessary…
Michelle Paret
I have two young children, and I work full-time, so my adult TV time is about as rare as finding a Kardashian-free tabloid. So I can’t commit to just any TV show. It better be a good one. I was therefore extremely excited when Netflix analyzed viewer data to find out at what point watchers get…
Davis Balestracci
“When I die, let it be in a meeting. The transition from life to death will be barely perceptible.” —Anonymous
Today I’m going to share some ideas from an always-thoughtful newsletter written by Steve Harden of LifeWings—a company of pilots who use aviation ideas to create cultures of safety in…
Douglas C. Fair
Sponsored Content
Statistical process control (SPC) software has been around for decades, used by manufacturers across industries to help monitor process behavior and control quality on the shop floor. Like any technology, the software has evolved over the years into something much more than a…
Eston Martz
I read trade publications that cover everything from banking to biotech, looking for interesting perspectives on data analysis and statistics, especially where they pertain to quality improvement.
Recently I read a great blog post by Tony Taylor, an analytical chemist with a background in…
William A. Levinson
We all know what happens when we assume. For example, traditional designed experiments assume that residuals, the differences between the actual and modeled data, follow the normal distribution (as seen in figure 1). These experiments include t tests, analysis of variance (ANOVA), factorial…
Jim Colton
How many samples do you need to be 95-percent confident that at least 95 percent—or even 99 percent—of your product is good? The answer depends on the type of response variable you are using—categorical or continuous.
The type of response will dictate whether you’ll use: 1. Attribute sampling:…
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…
