Knockout LLM Assessment: Using Large Language Models for Evaluations through Iterative Pairwise Comparisons

Isik Baran Sandan, Tu Anh Dinh, Jan Niehues


Abstract
Large Language Models (LLMs) have shown to be effective evaluators across various domains such as machine translations or the scientific domain. Current LLM-as-a-Judge approaches rely mostly on individual assessments or a single round of pairwise assessments, preventing the judge LLM from developing a global ranking perspective.To address this, we present Knockout Assessment, an LLM-as-a-Judge method using a knockout tournament system with iterative pairwise comparisons. Experiments across three LLMs on two datasets show that knockout assessment improves scoring accuracy, increasing Pearson correlation with expert evaluations by 0.07 on average for university-level exam scoring and machine translation evaluations, aligning LLM assessments more closely with human scoring.
Anthology ID:
2025.gem-1.10
Volume:
Proceedings of the Fourth Workshop on Generation, Evaluation and Metrics (GEM²)
Month:
July
Year:
2025
Address:
Vienna, Austria and virtual meeting
Editors:
Kaustubh Dhole, Miruna Clinciu
Venues:
GEM | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
121–128
Language:
URL:
https://preview.aclanthology.org/corrections-2025-08/2025.gem-1.10/
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Bibkey:
Cite (ACL):
Isik Baran Sandan, Tu Anh Dinh, and Jan Niehues. 2025. Knockout LLM Assessment: Using Large Language Models for Evaluations through Iterative Pairwise Comparisons. In Proceedings of the Fourth Workshop on Generation, Evaluation and Metrics (GEM²), pages 121–128, Vienna, Austria and virtual meeting. Association for Computational Linguistics.
Cite (Informal):
Knockout LLM Assessment: Using Large Language Models for Evaluations through Iterative Pairwise Comparisons (Sandan et al., GEM 2025)
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PDF:
https://preview.aclanthology.org/corrections-2025-08/2025.gem-1.10.pdf