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MLS-C01 Exploratory Data Analysis Practice Question

An ML engineer is performing EDA on a dataset of customer transactions. The dataset has 1 million rows and 20 columns, including a 'transaction_amount' column. The engineer notices that 5% of the transaction amounts are negative, which are data entry errors. The rest are positive. Which approach is most appropriate for handling these negative values during EDA?

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

Remove rows with negative transaction amounts from the dataset.

Removing rows with negative transaction amounts is the most appropriate approach during EDA. The negative values are data entry errors, not legitimate transactions. Removing them cleans the dataset without introducing bias from imputation or transformation. Option A is incorrect because imputing negative values with the median would treat the errors as missing data, but they are not missing; they are erroneous. This could distort the distribution. Option C is incorrect because taking absolute values would convert errors into positive values, adding noise and misrepresenting the data (e.g., a negative $100 error becomes a legitimate $100 transaction). Option D is incorrect because capping negative values at zero would create a spike at zero and distort the distribution, treating errors as valid zero amounts. Therefore, removal is the cleanest approach for erroneous data.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

  • Impute the negative values with the median of positive transaction amounts.

    Why it's wrong here

    Imputation is for missing data, not erroneous data.

  • Remove rows with negative transaction amounts from the dataset.

    Why this is correct

    Removing erroneous data points cleans the dataset without introducing bias.

  • Take the absolute value of the negative transaction amounts.

    Why it's wrong here

    This introduces bias by treating errors as valid high values.

  • Cap the negative values at zero.

    Why it's wrong here

    Capping at zero still includes erroneous zero values.

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