Statistics Features

Donald J. Wheeler's picture
Donald J. Wheeler
How can we use descriptive statistics to characterize our data? When I was teaching at the University of Tennessee I found a curious statement in a textbook that offered a practical answer to this...
Davis Balestracci's picture
Davis Balestracci
The Individuals chart is the “Swiss Army knife” of control charts. It usually approximates the supposedly “correct” chart under most conditions, and its use is much easier to understand and explain...
NIST's picture
NIST
On February 14, 1929, gunmen working for Al Capone disguised themselves as police officers, entered the warehouse of a competing gang, and shot seven of their rivals dead. The St. Valentine’s Day...
Donald J. Wheeler's picture
Donald J. Wheeler
Whenever we make a measurement, we have to decide how many digits to record. Traditional answers for this question are often little more than guesswork glorified by time. And with digital readouts...
Andrew Hwang's picture
Andrew Hwang
National discussions of crucial importance to ordinary citizens—such as funding for scientific and medical research, bailouts of financial institutions, and revised tax laws—inevitably involve...
Donald J. Wheeler's picture
Donald J. Wheeler
The precision to tolerance ratio is commonly used to characterize the usefulness of a measurement system. While this ratio is appealingly simple, it overstates the damage due to measurement error....
Donald J. Wheeler's picture
Donald J. Wheeler
Capability ratios are widely used and sometimes misunderstood. The computer will gladly offer up values of each of the commonly used capability and performance indexes. Yet there is little...
Mike Richman's picture
Mike Richman
Sustainable performance improvement is simply impossible without a firm handle on the precepts and tools of statistical process control (SPC). It is for this reason that we cover industrial...
Bonnie Stone's picture
Bonnie Stone
Lean, also known as “lean manufacturing” or “lean production,” focuses on maximizing customer value by removing waste and eliminating defects. Lean tools are about understanding the process,...
Eston Martz's picture
Eston Martz
Control charts take data about your process and plot it so you can distinguish between common-cause and special-cause variation. Knowing the difference is important because it permits you to...
Scott A. Hindle's picture
Scott A. Hindle
In theory, a production process is always predictable. In practice, however, predictable operation is an achievement that has to be sustained, which is easier said than done. Predictable operation...
Barbara A. Cleary's picture
Barbara A. Cleary
Taking time off for vacation seems to be a diminishing phenomenon among U.S. workers. Each year, Americans fail to use 662 million vacation days, and with those days $236 billion in economic...
Davis Balestracci's picture
Davis Balestracci
In my last column, I reflected back on my career to date and issued a challenge. Based on the relatively lukewarm response, let’s see whether I can engage a few more of you to join me on my...
Donald J. Wheeler's picture
Donald J. Wheeler
How do extra detection rules work to increase the sensitivity of a process behavior chart? What types of signals do they detect? Which detection rules should be used, and when should they be used...
John Flaig's picture
John Flaig
Story update 9/26/2017: The words "distribution of" were inadvertently left out of the last sentence of the second paragraph. Some practitioners think that if data from a process have a “bell-shaped...
Davis Balestracci's picture
Davis Balestracci
I have reached one of those life landmarks (receiving my Medicare card) and have been reflecting back... a lot. I will remain every bit as passionate about improvement and don’t think I will ever...
Eston Martz's picture
Eston Martz
The Six Sigma quality improvement methodology has lasted for decades because it gets results. Companies in every country around the world, and in every industry, have used this logical, step-by-...
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...
Eston Martz's picture
Eston Martz
Six Sigma is a quality improvement method that businesses have used for decades—because it gets results. A Six Sigma project follows a clearly defined series of steps, and companies in every...
Harish Jose's picture
Harish Jose
It’s been a while since I’ve written about statistics. So in this column, I will be looking at the rules of three and five. These are heuristics, or rules of thumb, that can help us out. They are...