SAS No. 26 Audit Sampling      

Status

Issued by Auditing Standards Committee in Taiwan on 30 June, 1994.

Summary

When designing audit procedures, the auditor should determine appropriate means for selecting items for testing so as to gather sufficient appropriate audit evidence to meet the objectives of the audit procedures.

Audit sampling involves the application of audit procedures to less than 100% of items within a class of transactions or account balance such that all sampling units have a chance of selection. This will enable the auditor to obtain and evaluate audit evidence about some characteristic of the items selected in order to form or assist in forming a conclusion concerning the population from which the sample is drawn. Audit sampling can use either a statistical or a non-statistical approach.  

The auditor should apply professional judgment in designing audit sampling and take into account the following:

  • The relationship of the sample to the relevant audit objective.
  • Population and sampling units.
  • Risks and confidence level.
  • Tolerable error.
  • Expected error in the population.
  • Stratification.

Sampling risk arises from the possibility that the auditor’s conclusion, based on a sample, may be different from the conclusion he would reach if the entire population were subjected to the same audit procedure.

Sample items should be selected in such a way that the sample can be expected to be representative of the population. This requires that all items in the population have an opportunity of being selected.

While there are a number of selection methods, three methods commonly used are:

  • Random selection,
  • Systematic selection, and
  • Haphazard selection.

Random selection ensures that all items in the population or within each stratum have a known chance of selection. Systematic selection involves selecting items using a constant interval between selections, the first interval having a random start. Haphazard selection may be an alternative to random selection provided that the auditor attempts to draw a representative sample from the entire population with no intention to either include or exclude specific units. 

Having carried out, on each sample item, those audit procedures that are appropriate to the particular audit objective, the auditor should:

  • Analyze any errors detected in the sample.
  • Project the errors found in the sample to the population, and
  • Assess the sampling risk.

The auditor should project the error results of the sample to the population from which the same was selected. When projecting error results, the auditor should keep in mind the qualitative aspects of the errors found.

The auditor should consider whether errors in the population might exceed the tolerable error by comparing the projected population error to the tolerable error and also then compare the sample result to the evidence obtained from other relevant audit procedures when forming his conclusions about an account balance, class of transactions or specific control.  

Having evaluated the sampling results, the auditor should conclude as to the extent to which he has obtained sufficient appropriate audit evidence in support of the particular characteristic of the account balance or class of transaction with which he is concerned.

Effective date

This Statement is effective for audit of financial statements with fiscal years ending on or after 31 December, 1996.

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