Audit sampling exists because of the impractical and costly effects of examining all or 100% of a client's records or books.
[1] Due to the negative effects produced by sampling risk, an auditor may have to perform additional procedures which in turn can impact the overall efficiency of the audit.
[4] Although exercising careful judgment is crucial during every step of the sampling process, it is extremely necessary when choosing the non-statistical approach.
This method does not include the use of tables or statistical percentages, but rather it relies upon professional judgment on the part of the auditor as well as the policy implemented by the firm.
Under this approach, it is common practice for most accounting firms to create universal guidelines for auditors in order to determine a proper sample size.