Validating LLM-as-a-Judge Systems under Rating Indeterminacy

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Hauptverfasser: Guerdan, Luke, Barocas, Solon, Holstein, Kenneth, Wallach, Hanna, Wu, Zhiwei Steven, Chouldechova, Alexandra
Format: Preprint
Veröffentlicht: 2025
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author Guerdan, Luke
Barocas, Solon
Holstein, Kenneth
Wallach, Hanna
Wu, Zhiwei Steven
Chouldechova, Alexandra
author_facet Guerdan, Luke
Barocas, Solon
Holstein, Kenneth
Wallach, Hanna
Wu, Zhiwei Steven
Chouldechova, Alexandra
contents The LLM-as-a-judge paradigm, in which a judge LLM system replaces human raters in rating the outputs of other generative AI (GenAI) systems, plays a critical role in scaling and standardizing GenAI evaluations. To validate such judge systems, evaluators assess human--judge agreement by first collecting multiple human ratings for each item in a validation corpus, then aggregating the ratings into a single, per-item gold label rating. For many items, however, rating criteria may admit multiple valid interpretations, so a human or LLM rater may deem multiple ratings "reasonable" or "correct." We call this condition rating indeterminacy. Problematically, many rating tasks that contain rating indeterminacy rely on forced-choice elicitation, whereby raters are instructed to select only one rating for each item. In this paper, we introduce a framework for validating LLM-as-a-judge systems under rating indeterminacy. We draw theoretical connections between different measures of judge system performance under different human--judge agreement metrics, and different rating elicitation and aggregation schemes. We demonstrate that differences in how humans and LLMs resolve rating indeterminacy when responding to forced-choice rating instructions can heavily bias LLM-as-a-judge validation. Through extensive experiments involving 11 real-world rating tasks and 9 commercial LLMs, we show that standard validation approaches that rely upon forced-choice ratings select judge systems that are highly suboptimal, performing as much as 31% worse than judge systems selected by our approach that uses multi-label "response set" ratings to account for rating indeterminacy. We conclude with concrete recommendations for more principled approaches to LLM-as-a-judge validation.
format Preprint
id arxiv_https___arxiv_org_abs_2503_05965
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Validating LLM-as-a-Judge Systems under Rating Indeterminacy
Guerdan, Luke
Barocas, Solon
Holstein, Kenneth
Wallach, Hanna
Wu, Zhiwei Steven
Chouldechova, Alexandra
Machine Learning
Computers and Society
Human-Computer Interaction
The LLM-as-a-judge paradigm, in which a judge LLM system replaces human raters in rating the outputs of other generative AI (GenAI) systems, plays a critical role in scaling and standardizing GenAI evaluations. To validate such judge systems, evaluators assess human--judge agreement by first collecting multiple human ratings for each item in a validation corpus, then aggregating the ratings into a single, per-item gold label rating. For many items, however, rating criteria may admit multiple valid interpretations, so a human or LLM rater may deem multiple ratings "reasonable" or "correct." We call this condition rating indeterminacy. Problematically, many rating tasks that contain rating indeterminacy rely on forced-choice elicitation, whereby raters are instructed to select only one rating for each item. In this paper, we introduce a framework for validating LLM-as-a-judge systems under rating indeterminacy. We draw theoretical connections between different measures of judge system performance under different human--judge agreement metrics, and different rating elicitation and aggregation schemes. We demonstrate that differences in how humans and LLMs resolve rating indeterminacy when responding to forced-choice rating instructions can heavily bias LLM-as-a-judge validation. Through extensive experiments involving 11 real-world rating tasks and 9 commercial LLMs, we show that standard validation approaches that rely upon forced-choice ratings select judge systems that are highly suboptimal, performing as much as 31% worse than judge systems selected by our approach that uses multi-label "response set" ratings to account for rating indeterminacy. We conclude with concrete recommendations for more principled approaches to LLM-as-a-judge validation.
title Validating LLM-as-a-Judge Systems under Rating Indeterminacy
topic Machine Learning
Computers and Society
Human-Computer Interaction
url https://arxiv.org/abs/2503.05965