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

The Deming Cycle, also known as PDCA, follows the sequence Plan, Do, Check, Act. 'Do' is the stage where the planned changes or improvements are implemented and executed on a small scale before full rollout. It is a foundational model used in ITIL's Continual Service Improvement.

Perform is not a stage in the Deming Cycle - the four stages are strictly Plan, Do, Check, and Act.

Implement is not one of the four named stages of the Deming Cycle, though implementation activities occur during the 'Do' stage.

Measure is not a distinct stage in the Deming Cycle - measurement activities are associated with the 'Check' stage.