Judging the Judges: A Systematic Study of Position Bias in LLM-as-a-Judge

Fuente: arXiv
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Main Authors: Shi, Lin, Ma, Chiyu, Liang, Wenhua, Diao, Xingjian, Ma, Weicheng, Vosoughi, Soroush
Format: Preprint
Published: 2024
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author Shi, Lin
Ma, Chiyu
Liang, Wenhua
Diao, Xingjian
Ma, Weicheng
Vosoughi, Soroush
author_facet Shi, Lin
Ma, Chiyu
Liang, Wenhua
Diao, Xingjian
Ma, Weicheng
Vosoughi, Soroush
contents LLM-as-a-Judge has emerged as a promising alternative to human evaluators across various tasks, yet inherent biases - particularly position bias, the tendency to favor solutions based on their position within the prompt - compromise its reliability. This exploratory study evaluates position bias in LLM judges across pairwise and list-wise comparison settings, introducing three metrics: repetition stability, position consistency, and preference fairness. Our experiments, involving 15 LLM judges across MTBench and DevBench with 22 tasks and approximately 40 solution-generating models, result in over 150,000 evaluation instances. We identify Judge-Level, Candidate-Level, and Task-Level factors contributing to bias. The findings confirm that position bias is not due to random chance and varies significantly across judges and tasks. While position bias is weakly influenced by the length of prompt components, it is strongly affected by the quality gap between solutions. Our agreement and disagreement analysis among judges further provides insights into the distribution of judging difficulty across the dataset, and highlights the potential for dataset modifications.
format Preprint
id arxiv_https___arxiv_org_abs_2406_07791
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Judging the Judges: A Systematic Study of Position Bias in LLM-as-a-Judge
Shi, Lin
Ma, Chiyu
Liang, Wenhua
Diao, Xingjian
Ma, Weicheng
Vosoughi, Soroush
Computation and Language
Artificial Intelligence
LLM-as-a-Judge has emerged as a promising alternative to human evaluators across various tasks, yet inherent biases - particularly position bias, the tendency to favor solutions based on their position within the prompt - compromise its reliability. This exploratory study evaluates position bias in LLM judges across pairwise and list-wise comparison settings, introducing three metrics: repetition stability, position consistency, and preference fairness. Our experiments, involving 15 LLM judges across MTBench and DevBench with 22 tasks and approximately 40 solution-generating models, result in over 150,000 evaluation instances. We identify Judge-Level, Candidate-Level, and Task-Level factors contributing to bias. The findings confirm that position bias is not due to random chance and varies significantly across judges and tasks. While position bias is weakly influenced by the length of prompt components, it is strongly affected by the quality gap between solutions. Our agreement and disagreement analysis among judges further provides insights into the distribution of judging difficulty across the dataset, and highlights the potential for dataset modifications.
title Judging the Judges: A Systematic Study of Position Bias in LLM-as-a-Judge
topic Computation and Language
Artificial Intelligence
url https://arxiv.org/abs/2406.07791