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Microlesson · 5-min read

Detection Risk – Sampling Risk & Non-Sampling Risk

## Detection Risk

### Definition

Detection Risk is the risk that the audit procedures performed will not detect a material misstatement that exists in an assertion.

Unlike IR and CR (entity risks), Detection Risk is the only component of Audit Risk that the auditor can control.

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### How to Reduce Detection Risk

The auditor can lower Detection Risk by:

1. Increasing the area of checking (broader coverage)

2. Testing larger samples (more representative)

3. Including competent and experienced personnel in the audit team

4. Changing the nature and timing of audit procedures

> Key principle: Higher ROMM → Accept lower Detection Risk → Increase extent/nature of audit work

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### Two Components of Detection Risk

#### 1. Sampling Risk

  • Risk that the auditor's conclusion, based on a sample, may be different from the conclusion if the entire population were tested
  • Arises because the sample is not representative of the whole population
  • Can be reduced by: selecting larger, statistically valid samples

#### 2. Non-Sampling Risk

  • Risk that the auditor reaches an erroneous conclusion for any reason other than sampling risk
  • Causes:
  • Applying an inappropriate audit procedure for the assertion
  • Misinterpreting audit evidence
  • Failing to recognize a misstatement even when evidence is obtained

> Example of Non-Sampling Risk: Auditor skips attending the physical inventory count (required by SA 501) and instead relies only on management's inventory listing. The procedure itself is inappropriate — this is non-sampling risk.

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### Detection Risk in Context of the Audit Risk Formula

$$\text{Audit Risk} = \text{ROMM} \times \text{DR}$$

ROMM LevelRequired DRAudit Response
HighMust be LowMore work, larger samples, senior staff
LowCan be relatively HigherLess extensive procedures

> Setting Detection Risk low means the auditor designs procedures to have a very high probability of detecting any misstatement that exists.

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### Summary Comparison

Inherent RiskControl RiskDetection Risk
Who controls it?Entity/NatureEntity/ICAuditor
When does it exist?Before the auditBefore the auditDuring the audit
How to reduce?Cannot be reduced by auditImprove IC (client's job)More/better audit procedures

Worked example

### Example 1

Sampling Risk Example:

An auditor tests 50 sales invoices out of 10,000. The sample happens to exclude all the month-end invoices where cut-off errors cluster. The conclusion from the sample is 'no misstatement' but the full population actually has significant cut-off errors. This is Sampling Risk — the sample was unrepresentative. Solution: use stratified random sampling with deliberate inclusion of high-risk periods.

### Example 2

Non-Sampling Risk Example:

An auditor needs to verify the existence of receivables (an asset assertion). Instead of sending confirmation letters to debtors (the appropriate procedure), the auditor only reviews internal sales ledger entries. This is an inappropriate procedure for the Existence assertion — any fictitious debtor would still appear in the ledger. This is Non-Sampling Risk.

### Example 3

DR Calibration Example:

Entity X is a fast-growing e-commerce startup (high IR on revenue) with no formal revenue recognition policy documented (high CR). ROMM on revenue is assessed as HIGH. To achieve acceptable overall Audit Risk of 5%, the auditor must design procedures with very LOW Detection Risk — e.g., 100% testing of large transactions, direct confirmation from payment gateways, and cut-off testing at year-end.

⚠️ Common exam mistakes

  • Thinking Detection Risk can be eliminated entirely — it can only be reduced, never to zero, because auditors use sampling and judgment.
  • Confusing Non-Sampling Risk with human error only — it also includes using systematically wrong procedures, not just individual mistakes.
  • Forgetting that DR is inversely related to audit effort — more audit work means lower DR (better chance of detecting misstatements).
  • Thinking sampling risk can be completely eliminated by taking a larger sample — even a large sample has some residual sampling risk unless 100% is tested.
Reference: SA 530 — SA 530 – Audit Sampling
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