Explanation
Plan: you decide what you want to achieve and how. Do: you carry out the plan, often small at first. Check: you measure and verify whether it works as intended. Act: you adjust, record what works well and start again. It is a circle, not a line: after Act a new Plan begins.
ISO 9001, ISO 14001 and ISO 45001 are built on this idea. You see it in the management cycle: setting policy and objectives, carrying out, measuring and internal auditing, and adjusting in the management review. A single improvement, such as a CAPA, often follows these steps too.
The common mistake is stopping after Do: the plan is carried out, but nobody checks whether it has an effect. Check and Act make the difference. That is why a measure comes with an effectiveness check and an objective with a measurement.
Example from practice
A department wants fewer slips: it plans anti-slip mats (plan), lays them down (do), counts the reports after a quarter (check) and decides to place the mats elsewhere too or choose a different solution (act).
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