Check, Act and Plan are three of the stages of the Deming Cycle. Which is the fourth?

The Deming Cycle, also known as the PDCA cycle, has 'Do' as its second stage, where the plan is executed and changes are implemented, typically on a small or trial scale. ITIL's Continual Service Improvement adopts the Deming Cycle as a core framework, with 'Do' representing the execution phase that bridges planning and the subsequent checking of results.

'Perform' is not a stage in the Deming Cycle; the four stages are specifically Plan, Do, Check, and Act.

'Implement' is not one of the four official Deming Cycle stages; the execution phase is named 'Do', not 'Implement'.

'Measure' is not a standalone stage in the Deming Cycle; measurement activity is encompassed within the 'Check' stage, not treated as a separate phase.