What Is Quality?
I recently started trying to go about how I might define quality. The task was to come up with an operational definition. This is an excellent example of something that sounds so obvious it should be trivial. For me, it has been anything but.
Operational Definitions
“An operational definition puts communicable meaning into a concept. Adjectives like good, reliable, uniform, round, tired, safe, unsafe, unemployed have no communicable meaning until they are expressed in operational terms of sampling, test, and criterion.” — Dr. W. Edwards Deming, Out of the Crisis, ch. 9
Effectively what is meant by an operational definition is a definition that includes a specific test (a specific requirement or specification), a criterion by which to assess a judgment, and a decision of yes or no, did it meet the criterion. In the agile software space, you could consider this to be much the same as a user story (the definition), the acceptance criteria (the assessment), and the qualification of doneness (is it done or not).
When talking about quality however, I’m after something that can pertain more to the product or the company at a higher aggregate level. Let’s look deeper into the meaning of quality before addressing that.
Dr. W. Edwards Deming
The concept of operational definitions was formalized by Dr. Deming. His System of Profound Knowledge (SoPK) is intimately tied to the definition of quality. On the one hand, it is an ideal condition we are targeting, quality. And on the other, SoPK is the method by which we can look to deliver towards that ideal.
The basic concepts that I believe Dr. Deming would emphasize when trying to define quality are clear criteria and having the ability to measure against that criteria. However, he would have stressed that quality isn't just about meeting specifications but also about satisfying customer needs and continually improving processes.
Maintaining low levels of defects or errors in products or services is paramount to delivering with quality. That alone is not sufficient though. Products and services are expected to continually innovate. Implementing new ideas and technologies to advance their quality. This cannot happen by maintaining some steady state. Regular analysis and enhancement of processes is required to improve effectiveness and in turn efficiency. All as integrated contributors to the definition of quality.
Dr. Joseph M. Juran
As a recent topic in our Profound Book Club, we read and discussed a chapter from Dr. Juran's writing, specifically from Juran’s Quality Handbook, 6th Edition. He was another of the masters focused on quality, so I considered this same question from his perspective.
Dr. Juran based his definition of quality around a product or service’s "fitness for purpose". This includes both meeting customer needs and having freedom from failures. Dr. Juran also notes that it must be delivered efficiently for superior business performance.
Dr. Juran further discussed having a systematic approach to managing quality, but this was discussed in service of quality as defined by fitness of purpose.
Dr. Genichi Taguchi
Dr. Taguchi is another master that has had a tremendous impact on quality improvement. Dr. Taguchi's definition of quality extends beyond the traditional view of meeting specifications and customer requirements to consider the broader societal impact. He defined quality as “the loss imparted to society from the time a product is shipped.”
An important contribution from Dr. Taguchi is the “Taguchi Loss Function.” This function quantifies quality as the cost to society of deviating from an ideal value. He emphasized the importance of "robustness” by designing products and processes that perform consistently under various conditions, including those beyond the manufacturer’s control.
Dr. Taguchi put a lot of emphasis on what he referred to as “Off-Line Quality Control,” which involves focusing on improving quality through better design rather than merely through inspection and control of manufacturing processes. This includes choosing to evolve to the best overall system design. It also includes parameter design, which is the optimizing design parameters to minimize variability. And finally, tolerance design to determine the acceptable ranges for these parameters.
An Operational Definition of Quality
Quality is the degree to which a product or service meets or exceeds customer expectations by being fit for its intended purpose and providing value. This includes delivering consistent performance, reliability, and ease of use, while minimizing defects. Quality includes continual improvement through feedback, innovation, and the emergent design of the product and its processes. The criteria for which are measured by both customer satisfaction and organizational efficiency.
Conclusion
The operational definition of quality is extremely relevant in today’s world and especially in the business of software delivery. Quality is not simply creating requirements documents, writing some code and then testing for compliance. It’s something more. Focusing on quality delivery and quality improvement requires being consistent and effective at improving the current state as well as innovating for the benefit of the customer and beyond.
Additional Resources
- Out of the Crisis by Dr. W. Edwards Deming
- Juran's Quality Handbook, 6th Ed. by Joseph M. Juran & Joseph A. De Feo
- Quality, 6th Ed. by Donna C. S. Summers
- v1.0.0 - Jul 14, 2024