## General Mnemonic for Extent of Checking: SIA DT

Letter	Factor
S	Size of the organization
I	State of Internal Control
A	Adequacy & reliability of books and records
D	Degree of desired confidence
T	Tolerable error range

---

## A. Factors for Tests of Controls (TOC)

Factor	Change	Effect on Sample Size
Assurance required from controls	↑ Increases	↑ Larger
Tolerable rate of deviation	↑ Increases	↓ Smaller
Expected rate of deviation	↑ Increases	↑ Larger
Desired assurance level	↑ Increases	↑ Larger
Population size (large population)	↑ Increases	Negligible

---

## B. Factors for Tests of Details (TOD)

Factor	Change	Effect on Sample Size
Auditor's assessed ROMMS	↑ Increases	↑ Larger
Reliance on other substantive procedures	↑ Increases	↓ Smaller
Desired assurance level	↑ Increases	↑ Larger
Tolerable misstatement	↑ Increases	↓ Smaller
Expected misstatement in population	↑ Increases	↑ Larger
Stratification applied	Applied	↓ Smaller
Population size	↑ Increases	Negligible

> Memory hook: Factors that increase confidence required or expected error → larger sample. Factors that increase tolerance or reliance on other work → smaller sample.

Worked example

### Example 1

Client has strong IT controls (low ROMMS). Auditor relies on other substantive analytical procedures. For TOD: both low ROMMS and high reliance on other procedures → sample size can be significantly reduced. If ROMMS were high and no other procedures used, sample would need to be much larger.

### Example 2

Auditor expects 2% deviation rate; tolerable rate = 5%. Sample size = 60. If client's deviation rate rises to 4% (still within tolerable, but closer to boundary), sample size must increase to perhaps 150 to maintain the same assurance level — expected rate moving toward tolerable rate increases sampling risk.

⚠️ Common exam mistakes

Higher tolerable misstatement/deviation → SMALLER sample (not larger) — students frequently get this direction wrong
Thinking population size always drives sample size — for large populations it has negligible effect; statistical sampling's efficiency comes from this property
Forgetting that stratification reduces sample size in TOD — students associate complexity with more work
Mixing TOC factors (deviation rates) with TOD factors (monetary amounts)

Reference: — SA 530 – Audit Sampling

Now that you've read this — what's next?

Move from understanding → mastery in 3 clicks. Each option below picks up from this lesson's topic.

🔥 Drill 5 Qs on this → ✍️ Adaptive practice →

Factors Influencing Sample Size – TOC and TOD

Worked example

⚠️ Common exam mistakes