Passage Summary: Claudette knows some obscure classical music that mostly only pros know, so the author assumes she must be a pro herself.

Conclusion: Claudette is almost certainly a classical pianist.

Reasoning: Claudette knows Clara Schumann's music, which is a trait shared by most classical pianists but very few people outside of that profession.

Analysis: This argument suffers from a base-rate fallacy. Even if a high percentage of a small group (pianists) has a trait, and a low percentage of a massive group (non-pianists) has it, there could still be more people in the massive group who have that trait simply because the group is so much larger. The author ignores the possibility that Claudette is just a well-informed music fan rather than a professional. Look for an error that describes confusing the probability of having a trait given a group with the probability of being in a group given a trait.