DA0-002 Data Acquisition and Preparation Practice Question
A data analyst is profiling a newly acquired customer dataset before loading it into a warehouse. The analyst notices that the 'country' column contains values such as 'USA', 'United States', 'U.S.A.', and 'US'. Which TWO actions are appropriate for standardizing this column during data preparation? (Choose two.)
⚠ Common exam trap
The trap here is believing that simple case and punctuation normalization is sufficient standardization, when synonyms like 'United States' still remain distinct without a mapping or reference standard.
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
✓
Use an ISO 3166 country code list as the reference and map each variant to its corresponding alpha-2 or alpha-3 code.
Standardizing a country column with known variants requires deterministic translation to a canonical form. A mapping table documents each variant explicitly, and ISO 3166 codes provide an authoritative reference that removes name ambiguity. Together they yield consistent values suitable for joins and aggregation. Normalization alone leaves synonyms unresolved, fuzzy clustering risks merging distinct entities, and deleting rows sacrifices valid data rather than cleaning it.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Delete rows that do not exactly match the most common value for the country column.
Why it's wrong here
Deleting non-matching rows discards valid customer records simply because of spelling variation, reducing data completeness and biasing analysis. The variants represent the same country and should be reconciled, not removed. This approach also scales poorly, since any new legitimate variant would cause data loss, and it does not produce a standardized column.
- ✓
Use an ISO 3166 country code list as the reference and map each variant to its corresponding alpha-2 or alpha-3 code.
Why this is correct
ISO 3166 provides an authoritative, unambiguous set of country codes, so mapping variants to alpha-2 or alpha-3 codes yields a stable, internationally recognized canonical form. It avoids ambiguity in names and supports reliable joins and aggregation. This is a best practice for country data standardization and complements a mapping table with an external standard.
- ✗
Apply a fuzzy matching algorithm to cluster similar strings and assign the most frequent value as the canonical form.
Why it's wrong here
Fuzzy matching can group similar strings, but choosing the most frequent variant as canonical is unstable and may pick an abbreviation rather than the preferred standard. Without deterministic rules and review, fuzzy clustering can merge distinct countries and introduce silent errors. It is useful for discovery, but not as the sole standardization method when exact variants are already known.
- ✗
Convert all values to uppercase and remove periods, then treat the results as distinct categories.
Why it's wrong here
Uppercasing and removing periods would turn 'U.S.A.' into 'USA', but 'United States' would remain different, so the column would still contain multiple representations of the same country. Treating them as distinct categories defeats standardization and causes incorrect counts and joins. Normalization alone does not resolve synonyms or abbreviations, so this does not achieve a single canonical value.
- ✓
Create a mapping table that translates each variant to a single canonical country name or code.
Why this is correct
A mapping table provides an explicit, auditable translation from known variants to a canonical value, which is maintainable and transparent. It handles abbreviations and alternate spellings without guessing and can be extended as new variants appear. This is a standard reference-data approach for country standardization and supports consistent grouping and joining across datasets.
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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
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