PDCL cycle




Demings PDCA cycle: rather a Shewhart-PDCL-cycle?

[PDCA: Plan, Do, Check, Act;
 PDCL: Plan, Do, Check, Learn]


Attempts for clarification on PDCA cycle should be called PDCL cycle and that PDCA originally is not based on Deming had been carried out several times. Recently an article of the journal QZ (Qualität & Zuverlässigkeit; English translation: quality and reliability) dealt with that issue [1]. As the abbrevation PDCA still is used all over the world and because the PDCA cycle still is attributed to William Edwards Deming (1900 - 1993), I would like to present the statements of the QZ article with my own words.

The origin of the PDCA cyclus is based in the 1930s, the inventor is Walter A. Shewhart, a teacher of Deming. But it is thanks to Deming that the PDCA cycle was manifestetd and made known, and since the 1950s especially in Japan the PDCA cycle was connected with Demings name. Since then this link between PDCA and Deming prevailed all over the world. Deming himself tried several times in his publications to point out that the origin of PDCA is based on Shewhart, but the general QM specialized literature always liaised Deming with the PDCA cycle.


Regarding the interpretation of the PDCA cycle mostly the step Act caused irritations. The PDCA concept, which is well-known as Deming cycle, lastly was changed by Deming himself into PDSA: Plan, Do, Study, Act. Here the step study - or even learn - may be recognized as the most important component within this cycle.

This may also lead to the so-called PDCL cycle, which also was mentioned by Deming: Plan, Do, Check, Learn. As an explanation: a possible change should be planned thoroughly, then the planned change needs to be done; The performed change will be checked on efficiacy and evaluated with the aim to learn from this change for further improvement. The PDCL cycle starts again and drives the QM world to continuous improvement!


Dietmar Barth
(German version: 29.04.2010)



  1. Learn first, then act - errors about the so-called Deming PDCA cycle
    journal: Qualität und Zuverlässigkeit;
    QZ 2009, volume 54, no. 10, p. 18-19
    (German; original title: Erst lernen, dann handeln - Irrtümer um den Demingschen PDCA-Zyklus


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