Excellent firms don’t believe in excellence – only in constant improvement and constant change.
– Tom Peters
The PDSA (Plan-Do-Study-Act) cycle is the core component of continuous improvement programs. You may have heard it called PDCA (Plan-Do-Check-Act), and they are very similar, but I have come to prefer PDSA for reasons I’ll explain shortly. Understanding the cycle, and it’s application to continuous improvement, is critical for leadership. But first, a history lesson.
Ronald Moen and Clifford Norman wrote a well-researched article in the November 2010 issue of Quality Progress that detailed the history behind PDCA and PDSA. The cycle has its origins in 1939 when Walter Shewhart created the SPI (Specification-Production-Inspection) cycle. This was geared toward mass production operations, but Shewhart soon realized the potential application to the scientific method of problem solving, writing “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 respectively to hypothesizing, carrying out an experiment and testing the hypothesis. The three steps constitute a dynamic scientific process of acquiring knowledge.”
At the time, W. Edwards Deming was working with Shewhart to edit a series of Shewhart’s lectures into what would become Shewhart’s Statistical Method from the Viewpoint of Quality Control, published in 1939. Deming eventually modified the cycle and presented his DPSR (Design-Production-Sales-Research) cycle in 1950, referred to as the Deming Cycle or Deming Wheel. According to Masaaki Imai, Toyota then modified the Deming Wheel into the PDCA (Plan-Do-Check-Act) cycle and began applying it to problem solving.
In 1983 Deming again revised the Shewhart Cycle, with another modification in 1993 to finally make it the PDSA (Plan-Do-Study-Act) Cycle, or what Deming called the Shewhart Cycle for Learning and Development. Deming continued to have issues with the PDCA Cycle. In 1990 he wrote Ronald Moen “Be sure to call it PDSA, not the corruption PDCA.” A year later he wrote “I don’t know the source of the cycle that you propose. How the PDCA ever came into existence I know not.”
The PDCA Cycle has not really evolved in the past 40 years and is still used today at Toyota. The PDSA Cycle continues to evolve, primarily in the questions asked at each stage. Although both embody the scientific method, I personally prefer the PDSA Cycle due to the “S” – Study – that is somewhat more intuitive than “C” – Check. Deming himself had a problem with Check as he believed it could be misconstrued as “hold back.”
So let’s take a look at each component of PDSA.
- Plan: Ask objective questions about the process and create a plan to carry out the experiment – who, what, when, where, and a prediction.
- Do: Execute the plan, take observations, and document problems and unexpected issues.
- Study: Analyze the data, compare to expectations, and summarize what was learned.
- Act: Adopt and standardize the new method if successful, otherwise identify changes to be made in preparation for starting the cycle over again with Plan.
It’s important to realize that the cycle is valuable at both process and organizational levels. For example, you started the Plan aspect of the cycle back in the Clarify section with understanding the current state and creating a hoshin plan. As you execute the annual and breakthrough objectives of the hoshin plan you are in the Do quadrant. On a regular basis you will evaluate the hoshin plan and the results of the goals as Study, and then modify as necessary, Act, for the next revision of the hoshin plan.
In this section I will discuss various problem solving and improvement tools and methods for process-scale improvements, but you’ll note that they all follow the same PDSA cycle.