Popularized by Deming and adopted by Toyota in the 1950s, the PDCA cycle is memorable method for problem solving towards continual improvement that uses four steps:

  1. Plan

  2. Do

  3. Check

  4. Adjust (also called Act)

With a little more detail on this pass:

  1. Plan. Sense an issue, define the problem, plan a small experiment, change or test, aimed at an objective like improvement, often form a testable prediction called a hypothesis, identify the who, what, when, where, why

  2. Do. Do the small experiment, change or test

  3. Check. Observe actual results and then compare to any predictions to see what the results tell us

  4. Adjust. Modify next actions based on what was learned from the feedback of the small experiment

The PDCA cycle has become the basis for evidence-based decision making in many organizations.

The original "A" was act in the Toyota version, but many use the alternate "A" word adjust. We think the word adjust better describes the action of modification based upon feedback, so we use adjust in this book. Use what you want for the A as long as you cycle through PDCA often enough to improve. The PDCA cycle is a simple way to use experimentation to continually improve your processes.

The PDCA cycle came to us from the domain of quality. PDCA was made popular by Dr. W. Edwards Deming, who is considered by many to be the father of modern quality control.[1]

During his lectures in Japan in the early 1950s, [1] Deming got the Japanese interested in his methods of quality control.[2]

Toyota calls it the PDCA cycle. It also became known as the Deming Cycle; although, Deming actually called it the Shewhart cycle after his mentor, Walter A. Shewhart, the originator of Statistical Process Control (SPC). You may hear it referred to by any of these names.

The U.S. War Department recognized Deming’s expertise in statistics and asked him to go to Japan in the late 1940s to study agricultural production and help with related problems in this war-damaged nation. In the 1950s, General Douglas MacArthur asked him to assist Japan with their census. Deming taught hundreds of Japanese engineers and industrial managers his ideas to help correct their quality problems.

The Japanese embraced Deming’s quality concepts and PDCA and used it to go from worst in quality in the 1950s to best in quality by the 1980s in multiple products. Deming had considerable influence in Japan. Their highest award for quality is called the Deming Prize. The rise of Japanese manufacturing from the 1950s to the 2010s was influenced by Deming’s efforts and his PDCA cycle which became widely used for improvement. After Japanese companies used Deming’s ideas to such great effect, American businesses took note, and many began to adopt Deming’s quality concepts in the 1980s.

All of this success in this domain has inspired the application of Deming’s PDCA cycle in other domains.

1. Reproduced from Wikipedia article https://en.wikipedia.org/wiki/PDCA under a Creative Commons Attribution-ShareAlike 3.0 license.
2. For more detail about how the Japanese used quality before the American automakers, see The Reckoning, by David Halberstam, 1986

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