Statistical Sampling
Calculate sample sizes based on population characteristics, confidence level, and tolerable misstatement. Compliant with ISA 530 — Audit Sampling.
Sampling parameters
Confidence level
Audit risk assessment
Sampling objective
Random number generator
Systematic selection
Monetary Unit Sampling (MUS)
Confidence level
Generate sampling documentation memo
ISA 530 — Audit Sampling Quick Reference
ISA 530 deals with the auditor's use of statistical and non-statistical sampling when designing and performing audit procedures.
Key definitions:
- Audit sampling — applying audit procedures to less than 100% of items, enabling conclusions about the entire population
- Sampling risk — risk that the auditor's conclusion based on a sample may differ from the conclusion if the entire population were tested
- Tolerable misstatement — maximum misstatement the auditor is willing to accept and still conclude the balance is not materially misstated
- Expected misstatement — amount of misstatement the auditor expects to find in the population
Sample size factors (ISA 530.A11):
- Higher confidence required → larger sample
- Lower tolerable misstatement → larger sample
- Higher expected misstatement → larger sample
- Larger population → marginally larger sample (diminishing effect above ~5,000)
- Stratification can reduce total sample needed
Selection methods (ISA 530.A13):
- Random — every item has equal probability of selection (preferred)
- Systematic — constant interval, random start (efficient for large populations)
- Monetary Unit (MUS) — probability proportional to size (detects overstatements)
- Haphazard — without structured technique (acceptable if no conscious bias)