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The History & Evolution of the PDSA Cycle of Improvement

Posted by Maggie Millard

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Jun 24, 2021 6:09:34 PM

A quote from Dr. Deming about the PDSA cycle on a background image of a green forest.The PDSA cycle is a popular approach to process improvement because of its simultaneous simplicity and effectiveness. PDSA cycles can be applied to an unlimited number of processes, making them applicable across almost every industry. We thought it was worth a quick look back at how it came to be and how it has changed over time.


What is the PDSA Cycle?

The PDSA cycle most broadly used today is a structured approach to improvement with four steps. It is a scientific, iterative approach to problem-solving that involves testing solutions, measuring results, and implementing positive change when a test of change works out well by our judgement.

Plan: During the planning step, the team determines what will be accomplished and outlines the current situation. They set the benchmarks for improvement and discuss potential solutions to be tested.

Do: Once there's a hypothesis about potential changes that will lead to measurable improvement, testing can begin. Process changes are introduced, and the results are observed objectively, using data when we can.

Study: During this phase, the results of the experimental improvement are collected and compared against the expected results. The data gathered is analyzed to determine if a measurable improvement was achieved and if it is in line with the expectations defined in the planning phase.

Act (Adjust): If the study confirms that an improvement that meets expectations has been achieved, the changed process becomes the baseline for future improvement cycles. The team updates Standard Work documents and performance expectations. 

The PDSA cycle (sometimes called the Lean PDSA cycle) is intended to be repeated as often as necessary as processes move ever closer to perfection.

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How was PDSA Developed?

Dr. W. Edwards Deming

Dr. Deming was an American engineer, statistician, and management consultant. He started his career as an electrical engineer, later specializing in mathematical physics. He is best known for his work in Japan’s auto industry after the second world war. He is considered, even today, to be the most influential non-Japanese person in the Japanese manufacturing industry. He championed the management principle of statistical process control, a precursor of Total Quality Management. It is not unusual for him to be partially credited with the rapid post-war economic rise of the Japanese economy.

The Shewhart Cycle

Deming was influenced by Walter Andrew Shewhart, an American physicist, engineer, and statistician. Shewhart’s book Statistical Method from the Viewpoint of Quality Control, published in 1939, first introduced the concept of a straight-line, three-step scientific process of specification, production, and inspection.

He wrote, “It may be helpful to think of the three steps in the mass production process as steps in the scientific method. In this sense, specification, production, and inspection correspond to hypothesizing, carrying out an experiment, and testing the hypothesis, respectively. These three steps constitute a dynamic scientific process of acquiring knowledge.” He eventually clarified that the steps should go in a circle rather than a straight line, and that concept became what is known as the Shewhart Cycle.

The Deming Wheel

Dr. Deming built off of Shewhart’s Cycle and modified it. In his new version of the Cycle, debuted in 1950, he stressed the importance of constant interaction among the four steps of design, production, sales, and research. This came to be known as the Deming Wheel or Deming’s Circle.


Illustration of the Deming Wheel including, Plan, Do, Study, Act.



Although it is somewhat unclear who made the changes or why, the Japanese executives modified Deming’s wheel into; Plan, Do, Check, Act (PDCA). This four-step cycle for problem-solving includes planning (a problem definition and a hypothesis about possible causes and solutions), doing (implementing), checking (measuring the results), and action (standardization if the results are satisfactory).


Deming was never fond of the PDCA cycle, noting that “check” in English is equated with “hold back.” Others point out that the word "check" may bias us to check or confirm that a test of change was good (as in "check that we tried it" instead of "check to see if it worked as we predicted"). In 1993 he introduced his new revision of the Shewhart cycle; Plan, Do, Study, Act (PDSA).


Wheel including, Plan, Do, Study, Act.


The Benefits and Challenges of the PDSA Model


Versatility: PDSA is helpful in a variety of business environments and for a wide array of processes. It can be used for project management, change control, product development, and resource allocation.

Simplicity: PDCA cycles are straightforward and easy to understand, yet they are a powerful force for meaningful improvement.

Consistency: Because the approach is so versatile, you can have a standard problem-solving methodology across the entire organization.


Difficulty: Although the approach is simple, doing the required work in a disciplined way isn’t easy, since we have old habits (such as jumping to solutions or assuming that changes will be positive). Team members often need coaching and some small wins before they trust that the effort is worth the reward and to help them break old habits. 

Leadership: PDSA is not a set-it-and-forget-it proposition. It is an ongoing, frequently repeated process that requires commitment and acceptance from the top down. Without effective leadership, the enthusiasm will wane over time.

Deming died in 1993, but his work lives on. Today, the PDSA approach is used by businesses across the globe to solve problems, improve quality, and enhance products. It’s a valuable tool brought to us by some of the world’s best thinkers in the science of process control and continuous improvement.

Topics: Daily Improvement, Lean

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