Lean Manufacturing and Six Sigma Definitions

Glossary terms, history, people and definitions about Lean and Six Sigma


Abbreviation for Plan Do Check Act, which is a model that provides a framework for the improvement of a process or system. It can be used to monitor a single issues or guide an entire improvement project or initiative. PDCA was made popular by W. Edwards Deming, who is considered by many to be the father of modern quality control. He always referred to it as the “Shewhart cycle”.

Establish objectives and processes in order to deliver the desired results. Requires a clear problem statement, data collection, observation and data analysis to identify variation sources or root causes. A plan is developed to experiment with ideas to see if they will improve the process or results.

Executes the plan developed from the previous step. Small changes are usually tested, and data is gathered to measure the effectiveness of the change.

Data and results gathered from the Do phase are evaluated. Data is compared to the expected outcomes to see any significant changes have occurred.

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. Planning for the next cycle can proceed with a better baseline.

Later in Deming’s career, he modified PDCA to “Plan, Do, Study, Act” (PDSA) because he felt that “check” emphasized inspection over analysis.

Modified PDCA cycle developed by Deming. He mentioned that the PDSA Cycle originated in his teaching in Japan in 1950. It appeared in the booklet “Elementary Principles of the Statistical Control of Quality” (JUSE, 1950; out of print). As shown in the book, The New Economics.

Taiichi Ohno took the acronym PDCA from Deming’s improvement cycle, but he decided that the cycle should start with Check, so it would be reordered as CAPD. He asserted that clearly understanding the current state and developing consensus during the Check phase is the most important step in organizational transformation,


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