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Data Preparation for Machine LearninghardMultiple ChoiceObjective-mapped

MLA-C01 Data Preparation for Machine Learning Practice Question

A data scientist is preparing text data for natural language processing (NLP). The corpus contains many rare words and typos. To reduce dimensionality and improve generalization, they decide to apply stemming and remove stop words. However, after training, the model performs poorly on domain-specific terms. What is the most likely cause?

⚠ Common exam trap

AWS often tests the misconception that lemmatization is always superior to stemming, but the trap here is that the root cause is the inappropriate application of both preprocessing techniques to domain-specific text, not the choice between stemming and lemmatization.

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

Both stemming and stop word removal are inappropriate for the domain

Both stemming and stop word removal are inappropriate for this domain. Stemming aggressively reduces words to their root forms, which can conflate distinct domain-specific terms (e.g., 'therapy' and 'therapist' both stem to 'therap'), losing critical semantic nuance. Stop word removal can discard words that carry domain-specific meaning (e.g., 'not' in medical negation or 'up' in 'tune-up' for maintenance), leading to poor generalization on specialized vocabulary.

Answer analysis

Option-by-option breakdown

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

  • The corpus should be lemmatized instead

    Why it's wrong here

    Lemmatization may help but does not address the stop word issue.

  • Both stemming and stop word removal are inappropriate for the domain

    Why this is correct

    In specialized domains, stemming can distort meaning and stop words can carry essential context.

  • Stemming is too aggressive for the domain

    Why it's wrong here

    While stemming could be aggressive, removing stop words could also be harmful; the combination is the issue.

  • Stop word removal removed important context words

    Why it's wrong here

    Stop word removal might remove domain-specific context, but stemming is also problematic; both together are likely the cause.

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Last reviewed: Jun 30, 2026

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