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Glossary/Audit procedures

Audit sampling

Audit sampling applies an audit procedure to less than 100 percent of the items in a population so that every sampling unit has a chance of selection, enabling conclusions about the whole population.

CORAA TeamUpdated November 5, 2026

Definition

Under AU-C 530, sampling means testing fewer than all items, with each unit having a chance to be selected, to reach a conclusion about the population. Sampling can be statistical, using random selection and probability theory to measure results, or nonstatistical, relying on judgment. Both need a clear objective, population, sample size and evaluation method.

Why it matters in an audit or review

The auditor cannot test everything, but must still reach a conclusion about the population. Sampling is one of three ways to select items for testing, along with testing all items and selecting specific items. Only sampling supports projecting results to the population. The sample must be representative, and the risk that it is not (sampling risk) is managed through size and design.

Example

A population of 4,500 customer invoices (illustrative) is tested for a pricing control. The auditor defines an invoice as the sampling unit, sets a tolerable deviation rate, uses a random number generator for 60 items and evaluates the deviations found against the tolerable rate.

Common mistakes

  • Calling a handful of handpicked items a sample and projecting from it.
  • Choosing sample size by habit instead of by risk, tolerable misstatement and expected misstatement.
  • Skipping the investigation of anomalies or errors.

FAQ

Is statistical sampling better than nonstatistical?

Neither is required. Statistical sampling quantifies sampling risk; nonstatistical needs enough judgment documentation to be defensible.

Sources

  • AICPA, AU-C Section 530, Audit Sampling
  • AICPA, AU-C Section 500, Audit Evidence (means of selecting items for testing)
  • AICPA, Audit Guide: Audit Sampling

Definitions paraphrase AICPA and FASB guidance; read the standard itself before relying on a requirement. Example figures are illustrative. This page is guidance, not professional advice. Report an error

Standards

AU-C 530

Related terms

  • Sampling risk
    Sampling risk is the risk that the auditor's conclusion based on a sample would differ from the conclusion reached if the same procedure were applied to the entire population.
  • Attribute sampling
    Attribute sampling estimates how often a defined characteristic occurs in a population, most often the rate at which a control was not followed, and compares that rate with a tolerable deviation rate.
  • Monetary unit sampling
    Monetary unit sampling is a statistical method in which each dollar in a population is a sampling unit, so larger items are more likely to be selected and the sample is weighted by value.
  • Random selection
    Random selection chooses sample items so that every item in the population has a known chance of selection, typically using a random number generator or random number table.

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