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Recall

As explained in Introduction to Generative AI, Second Edition

Recall is the proportion of actual positive cases that a classifier correctly identifies.

Recall is the proportion of actual positive cases that a classifier correctly identifies. It helps evaluate whether an LLM judge finds positive examples reliably, especially when overall accuracy could hide scarce “yes” labels. section 7.10

Recall appears in evaluation workflows that:

  • Compare an LLM’s binary annotations with labels supplied by a human expert. section 7.10
  • Assess whether an annotation prompt identifies the target quality with high recall and precision. section 7.10
  • Support comparisons among future changes to a system prompt after the judge has been validated. section 7.10

Real estate listing evaluation

An LLM judge labels generated real estate descriptions for enthusiasm or positivity. Recall indicates how often it identifies descriptions that expert annotators marked positive. section 7.10

Table 7.5 Possible types of scores in LLM evaluations

Score type

Description

Example prompt

Binary label

Given an output and one or more criteria to evaluate, the LLM judge assesses whether or not the output meets those criteria.

“Evaluate whether the output fulfills the user’s request. Answer yes or no.”

Classification

Given an output and a set of categories, the LLM judge classifies the output into the relevant category.

“Does the output 1) fulfill the user’s request completely (FULL), 2) fulfill the user’s request partially (PARTIAL), or 3) not fulfill the user’s request (NONE)? Answer FULL, PARTIAL, or NONE.

Numeric rating

Given an output and a rating scale, the LLM judge assigns the output a rating.

“On a scale of 1 to 5, how well does this output fulfill the user’s request?”

Ranking

Given multiple outputs and a set of criteria, the LLM judge ranks the outputs in order of preference.

“Which of these outputs best fulfills the user’s request?”

Evaluation scores can use binary labels, classifications, numeric ratings, or rankings; recall applies when labels form a classifier-style evaluation. section 7.10

How Introduction to Generative AI, Second Edition covers it

How deep it goes
Defines recall and applies it to classifier evaluation, while leaving the metric’s formula and implementation details implicit.
Examples
Uses binary expert labels for enthusiasm and positivity in generated real estate listing descriptions.
What it assumes
Assumes binary labels and basic classifier evaluation, while treating expert annotation as the comparison standard.
What you can do after
Evaluate annotation prompts and LLM judges for reliable positive-case detection against expert labels.
How it connects
Connects recall with precision, accuracy, classifier evaluation, and knowledge distillation.

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This explainer was generated by Manning's knowledge graph from the text of Introduction to Generative AI, Second Edition. The section links point to the parts of the book it draws on.