We’ve heard a lot about the Plan/Do/Check/Act (PDCA) and the Plan/Do/Study/Act (PDSA) Cycles. What are they? Are they different? Are they related?

We will first hear from two experts: The first, explaining PDCA and the second, explaining PDSA.

Then we’ll explore the history, differences, and relationship via an important paper that includes W.W. Edwards Deming’s view from one of the experts who worked with him. What did Deming think of the PDCA Cycle vs the PDSA Cycle?

Rich Schuttler, executive coach and management consultant, covers the Plan/Do/Check/Act Cycle. 

Plan: Formulate your objective and associated goals. Formulate the steps for carrying the plan out.

Do: Implement your plan

Check: Check the results of your plan

Act: Implement actions based on the results found

Cycle back to the Plan: How can we make it better?

Continue through the Cycle: This is the aim of continuous improvement

You can view Rich’s short video here.

Next, Ramon Cancino, M.D. explains Plan/Do/Study/Act cycle in this Mayo Clinic video.

Plan: Establish objectives and processes

Do: Implement the plan

Study: Assess collected and measured results

Act: Apply changes based on results

The PDSA Cycle was modeled after the Scientific Method.

Poorly designed PDSA Cycles “play a large role in the failure of quality improvement projects.”

The PDSA Cycle should be one part of a larger part of a process of improvement.

There are three questions that must be answered before PDSA:

  • What are we trying to accomplish?
  • How will we know that a change is an improvement?
  • What changes can we make that will result in improvement?

PDSA is a cycle. It doesn’t end after the first ACT step. The model for improvement is made up of multiple PDSA Cycles. This is continuous improvement.

You can view Dr. Cancino’s video here.

Now we will explore the history, the differences, and the relationship between PDCA and PDSA, and find out what Deming actually thought from Ron Moen, statistician and consultant who served as a helper in 70 four-day Deming seminars from 1983-1993 and as, director of statistical methods, managed Dr. Deming’s monthly visits to General Motors’ Pontiac Motor Division from 1982 – 1986.

In a paper by Ron Moen and Cliff Norman titled Cycling Back: Clearing up myths about the Deming Cycle and seeing how it keeps improving, Ron and Cliff discuss:

1. How did Deming’s PDSA evolve?

2. Did Deming create the plan-do-check-act (PDCA) cycle?

3. Are PDCA and PDSA related?

As mentioned earlier, PDSA is based on the scientific method. 

In their first figure, the authors summarize the evolution of the scientific method and the PDSA Cycle.


Later in their article, they say that “Over the years, Deming had strong beliefs about the PDCA cycle and clearly wanted to distinguish it from the PDSA cycle.”

Ron and Cliff go on to discuss the evolution of the PDSA Cycle.

You can access Ron and Cliff’s paper here. 

In a longer paper titled: Foundation and History of the PDSA Cycle, Ron gives more detail than appeared in the previous article.

You can access that paper here.

We hope that these two papers clear up the history and controversy surrounding PDSA vs PDCA.