CISA Information System Auditing Process Practice Question
An IS auditor uses statistical sampling to test a population of 10,000 transactions. The auditor discovers 5 errors in the sample of 200. Which of the following conclusions is most appropriate?
⚠ Common exam trap
CISA often tests the misconception that a sample error rate equals the population error rate, tempting candidates to pick the exact 2.5% figure instead of a confidence interval.
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 population error rate is likely between 1% and 4% at a given confidence level
Statistical sampling produces an estimate with a confidence interval, not a point value, so the correct conclusion is that the true population error rate likely falls within a range around the observed 2.5% (5/200). The option stating a range of 1% to 4% at a given confidence level correctly reflects that sampling results are probabilistic. The other options assert exact rates or draw conclusions about materiality that the sample alone cannot support.
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 population error rate is exactly 2.5%
Why it's wrong here
Statistical sampling provides an estimate, not an exact rate.
- ✗
The population has a material weakness
Why it's wrong here
Materiality depends on the error nature, not just rate.
- ✗
The population error rate is 5%
Why it's wrong here
No direct extrapolation without considering sampling error.
- ✓
The population error rate is likely between 1% and 4% at a given confidence level
Why this is correct
Five errors in 200 gives a 2.5% sample rate, and statistical projection applies a confidence interval around it. The range 1% to 4% reflects that sampling uncertainty, whereas a single point estimate would overstate precision.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official ISACA exam blueprint
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