The answer is to compute the frequency of each zip code. This is the most important EDA step before feature engineering for high-cardinality categorical features because it reveals the distribution of values across the 500 unique categories, directly informing encoding strategies like frequency-based grouping or target encoding. On the AWS Certified Machine Learning Specialty MLS-C01 exam, this question tests your understanding that linear models cannot handle high-cardinality categoricals natively, so EDA must focus on cardinality reduction rather than numeric checks like histograms or correlation. A common trap is confusing categorical EDA with continuous variable analysis—remember, zip codes are labels, not numbers. Memory tip: for high-cardinality categoricals, always "count before you encode" to avoid overfitting or sparse dummy variables.
MLS-C01 Exploratory Data Analysis Practice Question
This MLS-C01 practice question tests your understanding of exploratory data analysis. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company's dataset contains a feature 'zip_code' with 500 unique values. The data scientist wants to use this feature in a linear model. Which EDA step is most important before feature engineering?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Compute the frequency of each zip code
Because zip codes are categorical with high cardinality, analyzing the frequency distribution helps decide how to group or encode them (e.g., target encoding). Option A is wrong because histograms are for continuous variables. Option C is wrong because correlation is for numeric features. Option D is wrong because missing value proportion is unrelated to cardinality handling.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Check the proportion of missing values
Why it's wrong here
Missing value check is important but does not directly address cardinality.
✓
Compute the frequency of each zip code
Why this is correct
Knowing frequency helps decide which categories to combine or how to encode.
Related concept
Read the scenario before looking for a memorised answer.
✗
Plot a histogram of the feature
Why it's wrong here
Histograms are for continuous data; zip codes are categorical.
✗
Calculate the correlation between zip code and the target
Why it's wrong here
Correlation requires numeric data; zip codes are categorical.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
What to study next
Got this wrong? Here's your next step.
Identify which MLS-C01 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Exploratory Data Analysis — This question tests Exploratory Data Analysis — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Compute the frequency of each zip code — Because zip codes are categorical with high cardinality, analyzing the frequency distribution helps decide how to group or encode them (e.g., target encoding). Option A is wrong because histograms are for continuous variables. Option C is wrong because correlation is for numeric features. Option D is wrong because missing value proportion is unrelated to cardinality handling.
What should I do if I get this MLS-C01 question wrong?
Identify which MLS-C01 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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This MLS-C01 practice question is part of Courseiva's free Amazon Web Services 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 MLS-C01 exam.
Question Discussion
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