CISA Tolerable deviation rate Practice Question
An IS auditor is testing a control that requires two approvals for purchase orders over $10,000. The auditor selects a sample of 50 purchase orders from the population of 500. Using statistical sampling, the auditor finds 2 deviations. The tolerable deviation rate is 5%. What should the auditor conclude?
⚠ Common exam trap
A common trap is to believe that any deviation indicates control failure, but the conclusion depends on whether the sample deviation rate exceeds the tolerable rate.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The control is effective as the sample deviation rate is below the tolerable rate.
The sample deviation rate of 4% (2 out of 50) is below the tolerable deviation rate of 5%. Therefore, the control is considered effective based on the sample evidence. The auditor does not need to increase the sample size unless the deviation rate is close to the tolerable rate or other risk factors exist. In this case, the control can be relied upon as designed.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
The control is effective as the sample deviation rate is below the tolerable rate.
Why this is correct
The sample deviation rate of 4% is below the tolerable rate of 5%, indicating the control is effective.
- ✗
The auditor should increase the sample size to reduce sampling risk.
Why it's wrong here
Increasing sample size is not necessary because the sample deviation rate is already below the tolerable rate. The control can be relied upon as effective.
- ✗
The control is ineffective because deviations were found.
Why it's wrong here
Finding deviations does not automatically mean ineffective; the rate must be compared to the tolerable rate. Here, it is below, so the control is effective.
- ✗
The auditor should conclude that the control is ineffective and report a deficiency.
Why it's wrong here
The control is effective because the deviation rate is below the tolerable rate; reporting a deficiency is not warranted.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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