Statistics Article Features

W. Edwards Deming's picture
W. Edwards Deming
Editor’s note: The following is from a transcript of a forgotten speech given in Tokyo in 1978 by W. Edwards Deming for the Union of Japanese Scientists and Engineers (JUSE). Because the original was...
Donald J. Wheeler's picture
Donald J. Wheeler
One of the most common questions about any production process is, “What is the fraction nonconforming?” Many different approaches have been used to answer this question. This article will compare the...
Steve Moore's picture
Steve Moore
In this year’s April issue of the Bridge Bulletin, the ACBL (American Contract Bridge League) unveiled a new logo as part of a rebranding campaign to promote the beloved game of bridge to a wider...
Donald J. Wheeler's picture
Donald J. Wheeler
First, let it be known that all charts for count-based data are charts for individual values. Regardless of whether we are working with a count or a rate, we obtain one value per time period and want...
Jay Arthur—The KnowWare Man's picture
Jay Arthur—The KnowWare Man
There are many control chart rules to detect special causes (i.e., out-of-control conditions). Although most of these rules are clear, the one that seems to befuddle most people is the rule about...
Donald J. Wheeler's picture
Donald J. Wheeler
What do the shape statistics known as skewness and kurtosis tell us about our data? Last month we saw how the average and standard deviation define the balance point and radius of gyration for our...
William A. Levinson's picture
William A. Levinson
Part one of this article showed that it is possible, by means of a Visual Basic for Applications program in Microsoft Excel, to calculate the fraction of in-specification product that is rejected by...
William A. Levinson's picture
William A. Levinson
IATF 16949:2016 clause 7.1.5.1.1 requires measurement systems analysis (MSA) to quantify gage and instrument variation. The deliverables of the generally accepted procedure are the repeatability or...
Saligrama Agnihothri's picture
Saligrama Agnihothri
Health-tracking devices and apps are becoming part of everyday life. More than 300,000 mobile phone applications claim to help with managing diverse personal health issues, from monitoring blood...
Donald J. Wheeler's picture
Donald J. Wheeler
Your software routinely gives you four descriptive statistics for your data: the average, the standard deviation, the skewness, and the kurtosis. Of these only the average is easy to understand. This...
William A. Levinson's picture
William A. Levinson
The first part of this series introduced measurement systems analysis for attribute data, or attribute agreement analysis. AIAG1 provides a comprehensive overview, and Jd Marhevko2 has done an...
Donald J. Wheeler's picture
Donald J. Wheeler
Measurement error is ubiquitous. As a result, over the past 250 years, different areas of science and engineering have come up with many different ways to deal with the problem of measurement...
James Bossert's picture
James Bossert
When we talk about measurement system analysis (MSA), people tend to focus on attribute agreement analysis because it is usually quicker and easier to do than a gauge repeatability and...
William A. Levinson's picture
William A. Levinson
Measurement systems analysis (MSA) for attributes, or attribute agreement analysis, is a lot like eating broccoli or Brussels sprouts. We must often do things we don't like because they are necessary...
Ryan McKenna's picture
Ryan McKenna
To date, this series focused on relatively simple data analyses, such as learning one summary statistic about our data at a time. In reality, we’re often interested in a slightly more sophisticated...
Donald J. Wheeler's picture
Donald J. Wheeler
For more than 40 years it has been common to use the precision to tolerance ratio (P/T ratio) to compare the standard deviation of measurement error with the specified tolerance for a...
David Darais's picture
David Darais
In our last article, we discussed how to determine how many people drink pumpkin spice lattes in a given time period without learning their identifying information. But say, for example, you would...
Donald J. Wheeler's picture
Donald J. Wheeler
In my article, “Tightened 100% Inspection” (Quality Digest, March 29, 2021), we found that the excess costs associated with tightened specification limits are generally prohibitive. Here we...
David Darais's picture
David Darais
How many people drink pumpkin spice lattes in October, and how would you calculate this without learning specifically who is drinking them, and who is not? Although they seem simple or trivial,...
Donald J. Wheeler's picture
Donald J. Wheeler
Inspection sounds simple. Screen out the bad stuff and ship the good stuff. However, measurement error will always create problems of misclassification where good stuff is rejected, and bad stuff...