Continual improvement of a QMS can include actions to reduce variability of processes, products and services. So, a good starting point is about considering the results from analysis and evaluation (ISO 9001:2015 clause 9.1.3) and from management review (ISO 9001:2015 clause 9.3) in order to determine if continual improvement actions are needed.
The cycle of the left is the control cycle or the daily cycle. When you perform 9.1.3 or 9.3 you are checking performance (C) and deciding what to do (A).
If the decision is: we like this performance level we can keep the process without changes, you keep your internal standard (S) (procedures, rules, instructions). If the decision is: we must improve performance, you must jump into the improvement cycle, and perform the PDCA. You have to determine the root cause(s) and design a solution to remove them. That solution will be part of an action plan that must be implemented to change one or more processes of your QMS. Any relevant result of a QMS (desirable or undesirable) will always be the outcome of one or more processes. Removing the root cause(s) means changing, improving one or more processes. Like in this example:
The following material will provide you with information about root cause analysis and improvement:
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