The Deming Cycle

The Deming cycle, or PDCA cycle or PDSA, is a continuous quality improvement model consisting of a logical sequence of four repetitive steps for continuous improvement and learning: Plan, Do, Study (Check) and Act.( By Edwards Deming) The PDCA cycle is also known as the Deming Cycle, or as the Deming Wheel or as the Continuous Improvement Spiral. It originated in the 1920s with the eminent statistics expert Mr. Walter A. Shewhart, who introduced the concept of PLAN, DO and SEE. The late Total Quality Management (TQM) guru and renowned statistician Edwards Deming modified the Shewart cycle as: PLAN, DO, STUDY, and ACT.


Along with the other well-known American quality guru-Joseph Juran, Edwards Deming went to Japan as part of the occupation forces of the allies after World War II. Edwards Deming taught a lot of Quality Improvement methods to the Japanese, including the usage of statistics and the PLAN, DO, STUDY, ACT cycle.




The graphic above shows Deming's Plan-Do-Check-Act (PDCA) cycle. (Deming himself called it the 'Shewhart Cycle' but Deming's work in Japan has lead to it commonly being named after him.) In BPE, everything is done with the discipline of PDCA. At all levels of the organization we:


Plan what we are going to do. In this step we assess where we are, where we need to be, why this is important, and plan how to close the gap. Identify some potential solutions.


Do try out or test the solutions (sometimes at a pilot level).


Check to see if the countermeasures you tried out had the effect you hoped for, and make sure that there are no negative consequences associated with them. Assess if you have accomplished your objective.


Act on what you have learned. If you have accomplished your objective, put controls into place so that the issue never comes back again. If you have not accomplished your objective, go through the cycle again, starting with the Plan step.


Frequently, a particular project will define sub-objectives, run thorough the PDCA cycle one or more times to accomplish the sub-objective, then define the next objective and go through the cycle again. Thus, many projects end up "turning the wheel" many times before completion. In ongoing management activities, we find a similar use of the cycle.


What we are trying to avoid by using the PDCA discipline is the "Ready, Fire, Aim" fallacy where people jump to the solution without identifying the problem and assessing if their proposed solution fixes it, or even results in another problem. The Act step makes sure we don't have to fix it again in a couple of years.


Problems With Deming Cycle

The Deming Cycle's application was intended for quality control purposes and proposed continuous improvement in quality of products/experiments.[4] The simple cycle works well in this application, but it is debatable that it should be applied to major organizational improvement. ISO recognized the need to provide better guidance in this regard and published the ISO standard ISO 9004:2000, which replaced the use of the term continuous improvement with continual improvement. The change is not trivial, it recognizes that organizational quality system performance improvement requires significant effort and needs pauses to consolidate change (hence continual and not continuous improvement) (ISO 9004:2000).


The Deming Cycle has an inherent circular paradigm, it assumes that everything starts with Planning. Plan has a limited range of meaning. Shewart intended that experiments and quality control should be planned to deliver results in accordance with the specifications (see meaning above), which is good advice. However, Planning was not intended to cover aspects such as creativity, innovation, invention or Complex Adaptive Systems. In these aspects particularly when based upon imagination, it is often impossible or counterproductive to plan (see referenced Wikipedia pages for why this is so). Hence, PDCA is inapplicable in these situations.


The Deming Cycle approaches often do not get to the root cause of a problem, especially in adaptive situations which call for an experiential approach but demand much more rigour in analysis and data collection. An adaptive challenge exists where there are no visible solutions to problems, and can exist, for example in areas where chaos, uncertainty, and ambiguity exists, such as new frontiers, and existing complex systems such as Healthcare.


Do and Act have the same meaning in English. Dictionaries (Shorter Oxford) provide the following relevant definitions:


Do: verb 1 perform or carry out (an action). 2 achieve or complete (a specified target). 3 act or progress in a specified way. 4 work on (something) to bring it to a required state.


Act: verb 1 take action; do something. 2 take effect or have a particular effect. 3 behave in a specified way.


The 'Act' in the Deming Cycle is meant to be interpreted to have a different meaning to 'Do', otherwise it could be as easily have been PDCD or PACA. In PDCA, 'Act' is meant to apply actions to the outcome for necessary improvement (see meaning above), in other words 'Act' means 'Improve' (applying PDCA to itself could result in PDCI).


The Deming Cycle is a set of activities (Plan, Do, Check, Act) designed to drive continuous improvement. Initially implemented in manufacturing, it has broad applicability in business. First developed by Walter Shewhart, it is more commonly called the Deming cycle in Japan where it was popularized by Edwards Deming.


Deming Cycle is also known as Shewhart cycle, PDCA, Plan-Do-Check-Act