Professionals working on quality don’t usually discuss what it is. Instead, they assume a shared understanding that often isn’t there. Individuals with training in different approaches generalize from different experiences and talk past each other. In meetings, these divergent views are often not aired; in the uninhibited environment of social media, on the other hand, they often degenerate into insults and personal attacks. Let’s try and address this foundational issue. 

The Agreement of Reality with Expectancy

“Quality is the agreement of reality with expectancy.” This is the most compelling definition I ever heard. It was 1981. I was starting out as a semiconductor process engineer and training to lead QC circles. At one point, the instructor quoted Juran as saying this in a speech. I have never been able to verify that Juran actually said it but it is consistent with what he wrote in the Quality Handbook.

Double Entendre

In everyday language, the “expectancy” is that a product or service will be as advertised; in probability theory, it is the expected value of a random variable, as in “life expectancy.” The beauty of this conceptual definition of quality is that it supports both operational definitions.

The quality of goods and services is the degree to which users perceive them to meet expectations. You can research these expectations and design, produce, market, and support your offerings to influence these perceptions, without any guarantee of success.

You can reach out to users and you can work on product characteristics—measured variables and attributes— but there is no set of variables and attributes that can guarantee perceptions.

Ideally, these characteristics take the same value for all units of product or service. In reality, they vary between units, and you can model them as random variables with expected values. Then, the absence of variation between units is an alternate understanding of the agreement of reality with expectancy.

You Can’t Control a Perception

Shewhart and Deming struggled with this conundrum. In Economic Control of Quality of Manufactured Product (1931), Walter A. Shewhart devotes Chapter 4 to the “Definition of Quality,” but does not actually produce one. He acknowledges that there are many, only to assert that “in any case the measure of quality is a quantity which may take on different values.”

Juran , instead, introduced the concepts of true and substitute characteristics. True characteristics are what users seek, but it often not reducible to anything we can observe. Substitute characteristics are observable and usable as predictors of the true characteristics.

In pastry, the proof of the cake is in the eating, but it is destructive testing and a pastry shop cannot eat all its cakes. To check their quality, it must use measurable substitute characteristics, also known as proxies. If its diameter is off and it contains half as much sugar as it should, then it is certainly defective. On the other hand, just because it has the right diameter and sugar content does not mean it tastes good. See Introduction to Manufacturing, Figure 17.1:

Other Definitions

Let’s review what a few authors have said on this topic.

Definitions Associated with Juran

Juran’s name, like Deming’s, is frequently invoked in support of definitions that are hard to find in his own publications.

Definitions of Quality Attributed to Juran:

• “Fitness for use.” (Defense Acquisition University, US Government)
• “Quality is the agreement of reality with expectancy.” I am guilty of attributing this to Juran without being able to quote him on it.

Juran’s Own Words:

In Section 2.1 of his Quality Handbook (5th edition), J.M. Juran addresses the issue of defining quality head-on and provides answers.

He starts by acknowledging the usage that prevailed Into the early 20th century when high-end, luxury products were described as being of “higher quality” than low-end, basic products. Juran calls this quality “product features that meet customer needs.” This is as opposed to “freedom from deficiencies” in producing and delivering these products.

In the bulk of the quality literature the quality of a product is not based on its features or its position within a product line or the market it serves. It is strictly a function of how well it serves the customers who buy it. A luxurious, feature-rich product can be deficient and a basic product excellent.

There are a few exceptions, however. Noriaki Kano’s model, for example, is about selecting features in product design, not about preventing deficiencies in production or service.

Armand Feigenbaum’s Definition

Armand Feigenbaum coined Total Quality Control (TQC) in 1951. On p. 7 of the 3rd edition, he wrote:

“Product and service quality can be defined as: The total composite product and service characteristics of marketing, engineering, manufacture, and maintenance through which the product and service in use will meet the expectations of the customer.”

This is essentially what you get when you unpack “the agreement of reality with expectancy” in its non-probabilistic interpretation. The more concise version supports the probabilistic interpretation too.

Definitions Associated with Deming

Google turns up several definitions that various authorities attribute to Deming, but that I couldn’t find in Deming’s books. Then there is what Deming actually wrote.

Definitions Attributed to Deming

Following are two underwhelming examples:

• “Meeting or exceeding customer expectations.” (Defense Acquisition University, US Government). May assert that exceeding customer expectations is better than just meeting them. It isn’t always. The subject came up in a dried soup plant, where an engineer thought it was not a quality problem to accidentally put three meatballs in a box that was supposed to contain only two. “The customer will not complain,” he said. But what about raised expectations? The same customer may complain when finding only the standard two meatballs in the next box.
• “Good quality means a predictable degree of uniformity and dependability with a quality standard suited to the customer.” (Cambridge University Press, 978-0-521-51522-1 – Quality and Reliability in Engineering. Tirupathi R. Chandrupatla). You cannot refer to a “quality standard” in a sentence that purports to define quality. In addition, “a predictable degree of uniformity and dependability” calls for further explanation of what is meant by predictable, uniform, and dependable.

Deming’s Own Words

Deming himself discusses the subject in two books:

• In Out of the Crisis, Deming asks, “What is Quality?” on p. 168 and discusses it through p. 171 but does not answer the question.
• In The New Economics, on p.2, he says,

“A product or service possesses quality if it helps somebody and enjoys a good and sustainable market.”

“Helping somebody” is a low bar. The Windows operating system did help some people, but no reasonable user would call it a high-quality product. German trains do help passengers move, but their service quality is universally recognized as abysmal.

The requirement of a “good and sustainable market” excludes the possibility that a high-quality product could be a commercial failure. In fact, markets do not always recognize quality, and there are numerous examples of products of mediocre quality outselling better ones. You eventually have customers reporting product flaws when, unbeknownst to them, alternative products existed that were free of these flaws.

ASQ definition

The ASQ provides its official definition on their website:

“Quality denotes an excellence in goods and services, especially to the degree they conform to requirements and satisfy customers.”

This looks like the product of a committee with members insisting on including certain keywords. Including “conformance to requirements” looks like a concession to the Crosby school.

The definition should not say what quality denotes but what it is. This odd wording may be because, if they had said “quality is excellence,” then poor quality would have been “poor excellence,” whatever that means. More generally, saying what a human endeavor is differs from saying what it takes to be good at it. Its definition must allow you to say that an individual or an organization is bad at it.

Defining quality as “excellence” also calls for defining excellence, which the ASQ does as follows:

“Excellence is a measure of consistently superior performance that surpasses requirements and expectations without demonstrating significant flaws or waste.”

Substituting this for the word “excellence” turns their definition of quality into word salad:

“Quality denotes a measure of consistently superior performance that surpasses requirements and expectations without demonstrating significant flaws or waste in goods and services, especially to the degree they conform to requirements and satisfy customers.”

“On target with minimum variance,”

Some authors assert that quality means “on target with minimum variance,” and that only those who don’t get it disagree. These would include, for example, Sadao Nomura, who, in The Toyota Way of Dantotsu Radical Quality Improvement, tells his personal story of quality improvement in forklift manufacturing in the 2000s and 2010s, without ever mentioning “variance” or “statistics.” It’s all about organizing to prevent defects and responding to customer claims so they don’t recur.

In dictionaries, definitions are noun phrases, as in Webster’s about a wok:

“On target with minimum variance” is a sentence fragment but not a noun phrase. The wording implies that there is a numerical variable with a target value T that has a variance \sigma^2,  and therefore an expected value \mu and a standard deviation \sigma. “On target” seems to imply that it always takes the target value, in other words that \mu = T and \sigma = 0, making “with minimum variance” redundant.

“On target with minimum variance” is, in fact, just an inarticulate reference to the Taguchi methods in experiment design, which aim to find combinations of machine settings to minimize a quadratic function of the distance from a post-process measurement to its target value.

While the Taguchi methods were a breakthrough in process development, they are not the entire domain of quality. Whenever you check a part against thresholds, you use the loss function that is flat at 0 between the limits and a constant outside, not a quadratic loss function.

At best, these words point to a means of achieving quality, but they do not tell us what it is.

Other Definitions of Quality

As of 2024, the word “Quality,” is 2069 years old. Cicero coined it in his book Academica in 45 BCE, as a translation of the Greek “poiotetes.” What Cicero meant is not obvious from his words, but he seems to have been a systems thinker, in that his version of quality was what makes a system more than the collection of its parts. Over the ensuing millenia, quality has taken on a variety of meanings, mostly not related to manufacturing or even business in general.

Over the centuries, it has been used to designate nobles, and then, by the early 1800s, extended to outstanding tradesmen, like the Barber of Sevile: “Handyman of the city. Early in the workshop, I arrive at dawn. Ah, what a life, what a pleasure for a barber of quality!”

When describing people, it applies to attractive personality traits, like honesty. loyalty, or friendliness. But sometimes it is just characteristics with no value judgment attached, as in Robert Musil’s The Man Without Qualities. The literal translation of the German title would have been “The man without properties,” which would have wrongly suggested a person who doesn’t own real estate.

Webster’s lists 19 different meanings for “Quality” and also has an entry for “Quality Control,” which does not list any tools:

 

Japanese Versions

Given that, over the past 100 years, quality in goods and services has been primarily an American and Japanese story, we need to look at Japanese definitions.

The Japanese Literature on Quality

The Japanese literature on quality doesn’t dwell on its definition anymore than the American one. Kaoru Ishikawa didn’t bother with it in his Guide to Quality Control (1976), and neither did Shigeo Shingo In Zero Quality Control (1985) where he rebuts Ishikawa by rejecting all statistical methods. Decades later, in The Toyota Way of Dantotsu Radical Quality Improvement (2021), Sadao Nomura doesn’t define quality either.

The Answer in a Japanese Blog

On monodukuri.com, in 2023, Naohisa Imazawa wrote:

“Today, quality is generally interpreted in a broad sense from the perspective of customer satisfaction as the degree to which the product or service meets the customer’s prior expectations and enables the customer to be satisfied with the product or service.”

It’s a few more words than “Quality is the agreement of reality with expectancy,” but it is in the same spirit. The only nit I would pick is with the reference to “the customer,” a term I reserve for any economic agent who pays for goods or services and can switch suppliers.

I prefer the more general term “user” for a recipient of goods or services that may or may not meet these conditions. Treating the next operator on a line like a customer is good idea but it only makes a metaphorical customer, not an actual one. But that’s another discussion.

Japanese Dictionaries

Japan’s answer to Webster’s is the Kojien. The Japanese word for quality is “hinshitsu” (品質) and the Kojien defines it tersely as “the nature of a product,” based strictly on its etymology. “Hin” is short for “shinamono” (品物) or “product,” and “shitsu” for “seishitsu” (性質), or “nature” in the sense of property, characteristic, or disposition. It is too short, as the gap between a product’s nature and a user’s expectations is too wide.

The Japanese word does not carry the 2069-year baggage of the English word, with its multiple uses. On the other hand, it is specific to products, so how do you say “service quality”? Oddly, the Japanese word for service is borrowed from English, and “service quality is “sābisuhinshitsu” (サービス品質) another example of etymology as a poor guide to meaning.

The Kojien is more loquacious about Quality Control/Management. The same word, “Hinshitsukanri”(品質管理) is used for both control and management, and the Kojien defines it as follows:

“A business management method to stabilize and improve product quality, often conducted through small group activity, using control charts and other methods.” (経営管理方式の一、製品の品質の安定化および向上をはかること、管理図法のどの手法を用い、小集団活動として行われることが多い)

ChatGPT’s Definition of Quality

Asking the question to ChatGPT produced the following answer:

“Quality is a term that denotes the standard or degree of excellence of something. It is a measure of how good or desirable a product or service is in terms of meeting the expectations and requirements of the customer. Quality can encompass various aspects such as durability, reliability, performance, aesthetics, and customer satisfaction. In essence, it represents the superiority or superiority of a product or service relative to others in the market.”

A standard, a degree of excellence, and a measure are three different things. ChatGPT’s output is, as usual, underwhelming.

 

Conclusions

The quality of goods and services is a concept and needs a definition as such. Taguchi design of experiments, TQM, Run2Run controls, SPC, Precontrol, acceptance sampling, one-piece flow, Poka-Yoke, QRQC, Change Point Management, JKK, and others are technical and managerial tools each with a range of applicability. What they have in common is the purpose of maintaining and improving quality, and none of them encompasses the entire field.

References

• Cicero, M. T. (45 BCE). Academica. Germany: G. Olms.
• Deming, W. E. (2018). Out of the Crisis. United States: MIT Press.
• Deming, W. E. (2000). The New Economics: For Industry, Government, Education. MIT Press.
• Feigenbaum, A. V. (1951). Total quality control. United Kingdom: McGraw-Hill.
• Ishikawa, K. (1976). Guide to Quality Control. Japan: Asian Productivity Organization.
• Juran, J. M., Godfrey, A. B. (1999). Juran’s Quality Handbook. 5th Edition. McGraw-Hill Education.
• Musil, R. (1996). The man without qualities. Knopf Doubleday Publishing Group.
• Nomura, S. (2021). The Toyota Way of Dantotsu Radical Quality Improvement. Taylor & Francis.
• Shewhart, W. A. (1931). Economic Control of Quality of Manufactured Product. American Society for Quality Control.
• Shingo, S. (1985). Zero Quality Control: Source Inspection and the Poka-Yoke System. Taylor & Francis.

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