Shewhart cycle

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The Shewhart cycle is also known as the ‘plan-do-check-act’ cycle and was popularised by Edwards Deming who attributed it to W.A. Shewhart.

The cycle is a form of cybernetic control in a production environment but particularly lends itself to P3 management.

The cycle has four steps:Four stages of the Shewhart cycle

  • Plan
  • This step involves establishing expectations. In P3 management this is initially represented by the baselines produced by planning in the definition process.

  • Do
  • This represents the development of the objectives. At project level it is about work packages creating products. At programme level the principle is the same, it’s just that the work packages are the projects and the change management activity. Similarly, the work packages within a portfolio are projects and programmes.

    Within the ‘do' step data are collected about the progress of the work.

  • Check
  • Actual progress is now compared against the baseline. An important aspect of the cycle is that this step is not about simply tracking actual against baseline but also understanding the root causes of any differences. This understanding is the difference between progress data and progress information. It is information that is needed for the next step.

  • Act
  • If the differences between actual and baseline progress are within the appropriate tolerances, the relevant manager will take corrective action and plans will be updated. The cycle then returns to the first step.

    If progress is breaching, or is predicted to breach, tolerances then action will need to be escalated to a higher level. This is termed an ‘issue’ and is the link between first order and second order cybernetic control.


The principles of the Shewhart cycle are embodied in the activities of the Praxis delivery process.

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2nd September 2014Link to Italian page added

Shewhart cycle

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