DA0-002 Data Acquisition and Preparation Practice Question
A data analyst needs to perform stratified sampling on a customer database to ensure proportional representation across three regions: North (40%), South (30%), and West (30%). The total sample size required is 1,000. How many customers should be sampled from the North region?
⚠ Common exam trap
DA0-002 often tests whether candidates can apply the proportional allocation formula — the trap is confusing the region's percentage with the sample count or mixing up which region gets which share.
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
✓
400
Stratified sampling allocates sample size proportionally to each stratum's share of the population. North represents 40% of the population, so 40% of the 1,000-customer sample — 400 customers — should be drawn from North.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
333
Why it's wrong here
Sampling 333 customers ignores the stated 40% North proportion, yielding 33.3% instead. Stratified sampling allocates each stratum's share of the total: 40% of 1,000 is 400. The figure 333 is tempting because it equals an equal split of 1,000 across three regions, which would be correct only for equal-proportion strata.
- ✗
500
Why it's wrong here
500 represents half the sample, which matches no stratum proportion here. The North region's 40% share of 1,000 yields 400; 500 would over-represent North and distort the regional weighting the stratified design is meant to preserve.
- ✗
300
Why it's wrong here
300 misallocates the sample because it applies the South/West proportion to the North stratum. Stratified sampling requires each stratum's sample count to equal its population share multiplied by the total: North's 40% of 1,000 yields 400. Equal thirds would suit three equal-sized strata, not these unequal regions.
- ✓
400
Why this is correct
Stratified sampling allocates sample counts proportionally to each stratum's share of the population. North represents 40% of customers, so its allocation is 0.40 × 1,000 = 400. This satisfies the stem's proportional-representation constraint directly, giving North exactly its 40% share of the sample.
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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 CompTIA exam blueprint
This DA0-002 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the DA0-002 exam.