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Equation 15 · Measuring What a RAG System Retrieves, Not Just What It Answers

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kk

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kk

Symbol k

the scored by recall at.

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The practical consequence is that a retrieval-only evaluation is cheap to build once and reusable forever. A set of queries paired with the identifiers of the passages that answer them, scored by recall at k and nDCG, survives every later change to the generator, the prompt template, or the model vendor, because none of those changes touch the object being scored.

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