The Deming cycle, or PDSA cycle, 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.
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. Deming taught a lot of Quality Improvement methods to the Japanese, including the usage of statistics and the PLAN, DO, STUDY, ACT cycle.
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.