Critical thinking skills are essential for internal auditors when designing audit procedures and selecting samples. The situation described indicates that the auditor relied on a sampling method without thoroughly considering the potential risks and the specific context of the transaction population. Improved critical thinking skills would help the auditor better assess the representativeness of the sample, identify potential fraud risks, and ensure a more thorough and effective audit approach, potentially preventing the oversight that led to undetected fraud.

The IIA Standards: Standard 1220 – Due Professional Care: " Internal auditors must apply the care and skill expected of a reasonably prudent and competent internal auditor. Due professional care includes consideration of the use of technology-based audit and other data analysis techniques. "

IIA Practice Guide: " Assessing the Adequacy of Risk Management and Controls " : Emphasizes the importance of critical thinking in evaluating risks and controls.