A Brief History of PDSA
“ ... knowing begins and ends in experience; but it does not end in the experience in which it begins.” - C.I. Lewis
“Deming’s Plan, Do, Study, Act (PDSA) cycle is a process to gain empirical knowledge by applying and evaluating theories, formal or informal, in order to learn, to improve, and maybe by serendipity to innovate” - Edward Martin Baker
One could argue that the birth of PDSA began in the 17th century with the formalized use of the scientific method by Galileo Galilei and Francis Bacon. Although many came before them, Galileo Galilei, the father of modern science, and Francis Bacon, the father of empiricism. They advanced the use and ideas of the scientific method. Galileo established the usage of the scientific method through his experiments with objects in motion. On the other hand, Bacon made contributions in philosophy in the areas of theory of knowledge (epistemology). The majority of the previous scientific knowledge at the time was based on deductive reasoning. Bacon’s work focused more on inductive reasoning. To better comprehend the distinction, inductive reasoning draws broad generalizations from individual evidence, whereas deductive reasoning derives particular findings based on general hypotheses.
Near the end of the 19th century, several young academics from Harvard formed the "Metaphysical Club." This gathering would be the birthplace of the first American philosophy known as Pragmatism. Jabe Bloom, Ph.D. in Design Transition, describes Pragmatism as America's Jazz for philosophy. Whereas Jazz is a uniquely American form, Pragmatism is the first American-born philosophy. Merriam Webster defines Pragmatism as:
"An American movement in philosophy founded by C. S. Peirce and William James and marked by the doctrines that the meaning of conceptions is to be sought in their practical bearings, that the function of thought is to guide action, and that truth is preeminent to be tested by the practical consequences of belief."
The most famous pragmatist was Supreme Court Justice Oliver Wendell Holmes, mostly remembered for his "Shouting fire in a crowded theater" analogy. One of the things to help better understand Pragmatism is that it was created to respond to the unprecedented changes in American life near the end of the 19 century. The violence of the American Civil War and the European Enlightenment's optimism created room for a new American philosophy. Compounded with worldwide changes in science, including Darwin's "On the Origin of Species', Boltzman's Statistical Mechanics, and Max Planck's contributions to Quantum Mechanics. Also, all of this amid an American Industrial Revolution. This 19th-century American mindset provoked this group of American philosophers to create a need for new ways of thinking about knowledge and the world.
Probably the most influential individual related to the history of PDSA is a primarily unknown philosopher and pragmatist named Clarence Irving Lewis. Not to be confused with C.S. Lewis. C.I. Lewis created a lesser-known version of Pragmatism called "conceptual pragmatism." This contemporary form of Pragmatism made it more compatible with mathematics and natural sciences. Lewis stressed inductive empirical knowledge as a guide to understanding the world. At the risk of trying to explain an incredibly complex body of work described in Lewis' 1929 book, Mind, and the World Order, I'll try and summarize. By the way, Dr. Deming claimed he had to read Mind and the World Order six times before fully understanding it. In Mind and the World Order, Lewis explains the difference between a priori and a posteriori justification. Priori and a posteriori are Latin phrases used in philosophy to distinguish types of knowledge. A priori knowledge is independent of experience, and posteriori knowledge depends on empirical evidence. An example of a priori justification is something like 1 + 1 = 2.
A posteriori example will be if you add a liter of milk to an existing liter of milk, you have two liters of milk. The former model is based on an assumed truth. The prior requires empirical evidence.
Dr. Walter A. Shewhart is known to have described the first reference to the concept of PDSA in his 1939 book called "Statistical Method from the Viewpoint of Quality Control. Shewhart describes three steps in a dynamic scientific process of acquiring knowledge in what later became known as the Shewhart Cycle. In Mind and the World Order, Lewis describes knowledge as temporal, and therefore, it is required of us to make predictions to understand knowledge fully. The critical point is, Shewhart took Lewis' work and combined it with the ideas of manufacturing, measurements, and statistics.
Dr. Shewhart references C.I. Lewis' Mind and the World Order throughout his seminal work in Statistical Method from the Viewpoint of Quality Control. Dr. Shewhart created his famous Statistical Process Control (SPC) and his notions of PDSA a decade earlier; however, these ideas were not formally published until 1939.
Dr. Deming heard about Dr. Shewhart in the late 1920s as an intern at Hawthorne Works while Shewart created his initial ideas on SPC and PDSA. Dr. Shewhart had a profound effect on Dr. Deming. Deming later worked with Dr. Shewhart by inviting him to lecture at the Graduate School of the USDA. It was Dr. Shewhart who recommended Lewis' Mind and the World Order to Dr. Deming. Deming also references Lewis' Mind and World Order in his 1982 "Out of the Crisis." They were both heavily influenced by Lewis's work.
In 1950 Dr. Deming was invited to provide seminars on statistical quality control for the Japanese Union of Scientists and Engineers (JUSE). Around that time, Deming slightly modified the original Shewhart Cycle into a four-step process. The Japanese referred to this as the Deming Wheel. The Deming Wheel focused on a cycle of Design, Production, Sales, and Research/Redesign. An important point and insight into Deming's character were that he never referred to the cycle as the Deming Wheel or even PDCA. Deming was always clear that it was Shewhart's work.
One of the things that made Deming so successful in Japan was that he always taught Shewhart's ideas as a way of thinking and managing instead of just a set of statistical techniques. It's been said that Deming could explain Shewhart better than Shewhart. In some ways, Deming's true contribution to the world was that he could describe anyone better than they could describe their work. Deming always approached his teachings from a human perspective. He didn't see these ideas as tools; he saw them as concepts and approaches to better the human condition. Deming was always a huge proponent of the worker. His system worked very well with the Japanese eastern intrinsic nature and culture of continuous improvement.
An unnamed group of Japanese executives and academics later coined the first use of the Plan-Do-Check-Act (PDCA) cycle.
Mike Rother’s Toyota Kata describes how Toyota later added “Go and See” to the PDCA cycle. The idea of “Go and See” is described in the 2001 Toyota Way by Jeffrey Liker. In The Toyota Way, Liker explains Toyota’s 14 principles. Specifically in principle 12 - Go and see for yourself to thoroughly understand the situation (Genchi Genbutsu). This idea is also referred to as “Going to Gemba,” where Toyota would always check the actual condition every time no matter where they were in the cycle or how many times the condition had previously occurred.
In the 1980's Dr. Deming further modified the cycle by changing the "Check" to "Study," referring to the new cycle as PDSA. Deming felt that the difference between the western interpretation of "Check" versus the eastern interpretation was not really in line with the original intent of Shewhart's original cycle. Western interpretation of "Check" could imply stopping the cycle or viewing the experiment as a checkpoint or a gate for failure. At the same time, Shewhart's original intent was more in line with analyzing or studying the expected or unexpected results.
There is no such thing as a failed experiment, only experiments with unexpected outcomes. —R. Buckminster Fuller
The critical point of the "study" stage is that, as Buckminster Fuller implies, we learn from successes and failures equally and can always gain new insight and develop new capabilities from either.
The following is a modern template for the PDSA cycle:
Plan
Plan the test or observation, including a method for collecting data...
Do
Try out the test on a small scale.
Study
Set aside time to analyze the data and study the results.
Act
Refine the change based on what was learned from the test
In the 1990s, PDSA was used throughout the new Total Quality Movement TQM. Specifically, the Association in Process Improvement (API) created their "Model for Improvement" using the PDSA Cycle as a basis.
In Deming's last book, "The New Economics for Industry, Government, Education," first published in 1993, he put all of his 70 years of experience into a concept called System of Profound Knowledge (SoPK). Deming would describe SoPK as having a set of four lenses to understand complexity better. One of those lenses was called Theory of Knowledge. Dr. Deming died at 93, the same year his New Economics book was published. He was able to take all of his decades of learnings and influences and describe them in a single comprehensive theory he called SoPK.
A little less than two decades later, in 2009, Mike Rother further advanced the PDSA cycle in his book mentioned above, Toyota Kata. Rother explains the hidden side of Toyota in something he calls Improvement Kata. Chapter 6 illustrates Improvement Kata as a process of getting from a “Current Condition” to a “Target Condition” where the path is often unclear. He describes the path to the “Target Condition” as a nonlinear process and not always predictable.
Rother calls this the gray zone and uses a flashlight analogy to describe the process where he says that Toyota Production Systems used PDCA/PDSA as the flashlight.
In summary, PDSA is based on around 400 years of philosophy and science originating with the first use of the scientific method. Today it’s still an instrumental tool in healthcare, education, government, manufacturing, information technology, and general quality control.
My new book “Deming's Journey to Profound Knowledge” is now available on Amazon.
