For an action plan to be effective, it should be designed primarily to address which...

For an action plan to be effective, it must address the root cause of an observation. The root cause is the underlying reason why a problem or issue has occurred. By targeting the root cause, the action plan can help prevent the recurrence of the issue and ensure long-term resolution. Addressing only the condition or the symptoms of the problem may lead to temporary fixes, whereas understanding and resolving the root cause leads to more sustainable improvements.References:

Institute of Internal Auditors (IIA), Practice Guide – Root Cause Analysis.