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.
During EDA, a data scientist creates a scatter matrix of numerical features and notices that some features have a funnel-shaped pattern (variance increases with the mean). What is the appropriate transformation to stabilize variance?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Apply log transformation.
A funnel-shaped pattern in a scatter matrix indicates heteroscedasticity, where variance increases with the mean. The log transformation is appropriate because it compresses the scale of the data, making the variance more constant across the range of values, which stabilizes variance for right-skewed or multiplicative data.
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.
✓
Apply log transformation.
Why this is correct
Log transformation stabilizes variance when variance increases with mean.
Related concept
Read the scenario before looking for a memorised answer.
✗
Standardize the features using Z-scores.
Why it's wrong here
Standardization does not fix heteroscedasticity.
✗
Apply a sine transformation.
Why it's wrong here
Sine transformation is not for variance stabilization.
✗
Apply Box-Cox transformation with lambda=0.
Why it's wrong here
Box-Cox with lambda=0 is log, but the question asks for appropriate; log is more straightforward.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between transformations that stabilize variance (log, Box-Cox) versus those that only standardize (Z-scores) or are domain-specific (sine), and candidates may incorrectly choose Box-Cox with lambda=0 thinking it is a separate technique, missing that the log transformation is the canonical answer for funnel-shaped heteroscedasticity.
Detailed technical explanation
How to think about this question
The log transformation is a variance-stabilizing transformation (VST) derived from the Taylor series expansion, where if the standard deviation is proportional to the mean, the log makes the variance approximately constant. In practice, this is common in financial data (e.g., stock prices) or biological counts, where multiplicative errors dominate. The Box-Cox transformation generalizes this with lambda=0 for logs, but the log transformation is the direct and simplest choice for this pattern.
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.
TExam Day Tips
→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 exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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: Apply log transformation. — A funnel-shaped pattern in a scatter matrix indicates heteroscedasticity, where variance increases with the mean. The log transformation is appropriate because it compresses the scale of the data, making the variance more constant across the range of values, which stabilizes variance for right-skewed or multiplicative data.
What should I do if I get this MLS-C01 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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