What should an auditor focus on to ensure evidence is appropriate?

An auditor should prioritize the reliability and relevance of the audit evidence to ensure it is appropriate. Reliability refers to the trustworthiness of the evidence obtained, which can depend on its source and the methods used to gather it. Evidence that is obtained from independent external sources or through rigorous internal controls is generally more reliable. Relevance, on the other hand, denotes how closely the evidence pertains to the specific assertions being tested in the audit. Both factors are critical because strong, appropriate evidence directly enhances the auditor's conclusions and ultimately supports the overall audit opinion.

While considerations such as cost and availability, the volume of transactions tested, and the timeliness of evidence collection are important in an audit context, they do not directly address the appropriateness of the audit evidence itself. Cost concerns might lead to efficient use of resources, volume can help improve the generalizability of conclusions, and timeliness ensures that the evidence reflects current conditions. However, none of these factors can substitute for the need to have evidence that is both reliable and relevant, which remains the cornerstone of audit quality and effectiveness.