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Iterative design and management method used in business

PDCA or plan–do–check–act (sometimes called plan–do–check–adjust) is an iterative design and management method used in business for the control and continual improvement of processes and products. It is also known as the Shewhart cycle, or the control circle/cycle. Another version of this PDCA cycle is OPDCA. The added "O" stands for observation or as some versions say: "Observe the current condition." This emphasis on observation and current condition has currency with the literature on lean manufacturing and the Toyota Production System. The PDCA cycle, with Ishikawa's changes, can be traced back to S. Mizuno of the Tokyo Institute of Technology in 1959. Deming found that the focus on Check is more about the implementation of a change, with success or failure. His focus was on predicting the results of an improvement effort, studying the actual results, and comparing them to possibly revise the theory.

Establish objectives and processes required to deliver the desired results.

Carry out the objectives from the previous step.

Also called "adjust", this act phase is where a process is improved. Records from the "do" and "check" phases help identify issues with the process. These issues may include problems, non conformities, opportunities for improvement, inefficiencies, and other issues that result in outcomes that are evidently less than optimal. Root causes of such issues are investigated, found, and eliminated by modifying the process. Risk is re evaluated. At the end of the actions in this phase, the process has better instructions, standards, or goals. Planning for the next cycle can proceed with a better baseline. Work in the next do phase should not create a recurrence of the identified issues; if it does, then the action was not effective.

Plan–do–check–act is associated with W. Edwards Deming, who is considered by many to be the father of modern quality control; however, he used PDSA (Plan Do Study Act) and referred to it as the "Shewhart cycle". Later in Deming's career, he modified PDCA to "Plan, Do, Study, Act" (PDSA) because he felt that "check" emphasized inspection over analysis. The PDSA cycle was used to create the model of know how transfer process, and other models. The concept of PDCA is based on the scientific method, as developed from the work of Francis Bacon (Novum Organum, 1620). The scientific method can be written as "hypothesis–experiment–evaluation" or as "plan–do–check". Walter A. Shewhart described manufacture under "control"—under statistical control—as a three step process of specification, production, and inspection. He also specifically related this to the scientific method of hypothesis, experiment, and evaluation. Shewhart says that the statistician "must help to change the demand [for goods] by showing [ ] how to close up the tolerance range and to improve the quality of goods." Deming preferred plan, do, study, act because "study" has connotations in English closer to Shewhart's intent than "check". A fundamental principle of the scientific method and plan–do–check–act is iteration—once a hypothesis is confirmed (or negated), executing the cycle again will extend the knowledge further. Repeating the PDCA cycle can bring its users closer to the goal, usually a perfect operation and output. Toyota and other lean manufacturing companies propose that an engaged, problem solving workforce using PDCA in a culture of critical thinking is better able to innovate and stay ahead of the competition through rigorous problem solving and the subsequent innovations. One can envision an open coil spring, with each loop being one cycle of the scientific method, and each complete cycle indicating an increase in our knowledge of the system under study. This approach is based on the belief that our knowledge and skills are limited, but improving. Especially at the start of a project, key information may not be known; the PDCA—scientific method—provides feedback to justify guesses (hypotheses) and increase knowledge. Rather than enter "analysis paralysis" to get it perfect the first time, it is better to be approximately right than exactly wrong. With improved knowledge, one may choose to refine or alter the goal (ideal state). The aim of the PDCA cycle is to bring its users closer to whatever goal they choose. In the United States a PDCA approach is usually associated with a sizable project involving numerous people's time, and thus managers want to see large "breakthrough" improvements to justify the effort expended. However, the scientific method and PDCA apply to all sorts of projects and improvement activities.