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LLM evaluation judges exhibit position bias, skewing results

A common issue in evaluating Large Language Models (LLMs) using a judge model is position bias, where the judge favors the answer presented first, regardless of its quality. This bias can significantly skew reported win-rates, as demonstrated by an experiment where swapping answer order changed a model's win-rate by 15 percentage points. Research from Zheng et al. in their paper 'Judging LLM-as-a-Judge with MT-Bench and Chatbot Arena' (NeurIPS 2023) confirms this systematic preference in strong judges, including GPT-4. To mitigate this, evaluations should present each pair of answers in both possible orders to accurately measure content quality rather than prompt-induced bias. AI

IMPACT Highlights a critical flaw in LLM evaluation, urging developers to implement bidirectional comparisons to ensure accurate performance metrics.

RANK_REASON The item discusses a research finding about LLM evaluation methodology and cites a specific academic paper. [lever_c_demoted from research: ic=1 ai=1.0]

Read on dev.to — LLM tag →

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LLM evaluation judges exhibit position bias, skewing results

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  1. dev.to — LLM tag TIER_1 English(EN) · Maya Andersson ·

    Your LLM-as-judge has a position bias you are not measuring

    <p>If your pairwise judge sees answer A before answer B, it tends to prefer A. If you never swap the order, every win-rate you report is contaminated by which slot you happened to put each answer in.<br /> The first time I actually measured this, I did not believe the number. I h…