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The Origins of the Deming Wheel

The Plan-Do-Check-Act cycle has its origins the 1920s, with the work of American engineer and physicist, Walter Shewhart, and the development of his Statistical Process Control (SPC). Shewhart's original cycle - referring to manufacturing under statistical control - consisted of a three-step process of specification, production and inspection, which he suggested was analogous to the scientific method of hypothesis-experiment-evaluation.

This cycle was discussed in depth by W. Edwards Deming, who would refer to it as the " Shewhart Cycle " during his teaching in Japan during the post-war period. Deming believed that the cycle envisaged by Shewhart could be used during any process of continuous improvement, rather than merely in the manufacturing and engineering industry as Shewhart had originally designed it.

Plan-Do-Check-Act Cycle

Whilst acting as a professor in Japan, he taught a variant of Shewhart's cycle, Plan-Do-Study-Act (PDSA) - it was his participants who simplified the process to "Plan-Do-Check-Act", which he later referred to as a "corruption". However, it would be Plan-Do-Check-Act which would become popularised, and later known as " The Deming Wheel ".

Using the Plan-Do-Check-Act Cycle (PDCA)

The stages of PDCA are comparable with steps in the scientific method, and can similarly be utilised for a number of "experimental" or critical thinking tasks. It can be used by individuals and organisations to continually innovate, improve, or to stay ahead of market competition.

It is designed as a four-stage system which can be utilised to go from the unproductive " problem-faced " to the productive "problem-solved ". The four stages, though already mentioned, are:

  1. Plan - brainstorm and subsequently develop a relatively-concrete plan for any necessary positive changes and improvements.
  2. Do - implement some of your changes, but begin by introducing them on a small scale in order to test their efficacy whilst attempting to minimise any major disruptions to routine activity.
  3. Check (or Study) - monitor and assess whether the small, incremental changes are having the intended effect, and any unexpected side-effects - make sure to regularly check on regular key activities to ensure you understand the quality of the output and can identify any new issues as they occur.
  4. Act - if the "experiment" was successful, begin to implement these changes on a broader scale, making it part of your routine activities - make sure to involve and cooperate with any other individuals whom the changes may affect, or whose involvement you require in order to successful implement your initiative.

The most important facet of the PDCA cycle is that it is iterative - it can, and should be repeated until the problem is solved. It can, therefore, facilitate both major innovative jumps and small, incremental improvements (see Kaizen ). In the case of the latter, it can be used to prevent "analytical paralysis" - attempting to search directly for a wholescale change which could potentially result in improvement. It is an effective technique for ensuring return on major innovation projects involving multiple individuals.


The Health and Safety Executive (HSE) cite PDCA as an effective method for balancing systems and behavioural aspects of management to produce effective health and safety policy or risk management changes.