Statistical Sampling

Statistical sampling uses mathematical formulas to determine sample sizes and evaluate results with measurable confidence levels. AIIA supports multiple statistical sampling methods for audit testing.

Sampling Methods

Attribute Sampling

Tests whether a specific attribute is present (e.g., "Was the invoice approved?")

Parameters:

• Population size — total number of items
• Expected error rate — anticipated exception percentage
• Confidence level — typically 90% or 95%
• Tolerable error rate — maximum acceptable exception rate

Monetary Unit Sampling (MUS)

Tests for monetary misstatements in financial populations.

Parameters:

• Population value — total monetary value
• Materiality — tolerable misstatement amount
• Expected misstatement — anticipated error amount
• Confidence level — typically 90% or 95%

Discovery Sampling

Used when the expected error rate is zero — designed to detect at least one exception if it exists.

Parameters:

• Population size — total items
• Confidence level — probability of finding at least one error
• Critical rate — maximum acceptable error rate

Using Statistical Sampling

Step 1 — Define Parameters

1. Navigate to Sampling → + New Sample
2. Select the sampling method
3. Enter the required parameters
4. The system calculates the required sample size

Step 2 — Generate Sample

1. Click Generate Sample
2. The system randomly selects items from the population
3. Selection uses a cryptographically secure random number generator
4. The sample list is created with item references

Step 3 — Execute Testing

For each sampled item:

1. Test the item against the criteria
2. Record the result (Pass/Fail)
3. Document any exceptions
4. Link evidence if needed

Step 4 — Evaluate Results

The system evaluates results by:

• Calculating the observed error rate
• Comparing against the tolerable error rate
• Computing the upper error limit
• Providing a conclusion (acceptable/unacceptable)

Permissions

Action	Auditor	Manager	CAE
Create samples	✅	✅	✅
Generate sample	✅	✅	✅
Record test results	✅	✅	✅
View sample details	✅	✅	✅