Understanding the Impact of Confidence in Retrieval Augmented Generation: A Case Study in the Medical Domain

Shintaro Ozaki, Yuta Kato, Siyuan Feng, Masayo Tomita, Kazuki Hayashi, Wataru Hashimoto, Ryoma Obara, Masafumi Oyamada, Katsuhiko Hayashi, Hidetaka Kamigaito, Taro Watanabe


Abstract
Retrieval Augmented Generation (RAG) complements the knowledge of Large Language Models (LLMs) by leveraging external information to enhance response accuracy for queries. This approach is widely applied in several fields by taking its advantage of injecting the most up-to-date information, and researchers are focusing on understanding and improving this aspect to unlock the full potential of RAG in such high-stakes applications.However, despite the potential of RAG to address these needs, the mechanisms behind the confidence levels of its outputs remain underexplored.Our study focuses on the impact of RAG, specifically examining whether RAG increases the confidence of LLM outputs in the medical domain.We conduct this analysis across various configurations and models.We evaluate confidence by treating the model’s predicted probability as its output and calculating several evaluation metrics which include calibration error method, entropy, best probability, and accuracy.Experimental results across multiple datasets confirmed that certain models possess the capability to judge for themselves whether an inserted document relates to the correct answer. These results suggest that evaluating models based on their output probabilities determine whether they function as generators in the RAG framework.Our approach allows to evaluate whether the models handle retrieved documents.
Anthology ID:
2025.bionlp-1.1
Volume:
ACL 2025
Month:
August
Year:
2025
Address:
Viena, Austria
Editors:
Dina Demner-Fushman, Sophia Ananiadou, Makoto Miwa, Junichi Tsujii
Venues:
BioNLP | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
1–17
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URL:
https://preview.aclanthology.org/acl25-workshop-ingestion/2025.bionlp-1.1/
DOI:
Bibkey:
Cite (ACL):
Shintaro Ozaki, Yuta Kato, Siyuan Feng, Masayo Tomita, Kazuki Hayashi, Wataru Hashimoto, Ryoma Obara, Masafumi Oyamada, Katsuhiko Hayashi, Hidetaka Kamigaito, and Taro Watanabe. 2025. Understanding the Impact of Confidence in Retrieval Augmented Generation: A Case Study in the Medical Domain. In ACL 2025, pages 1–17, Viena, Austria. Association for Computational Linguistics.
Cite (Informal):
Understanding the Impact of Confidence in Retrieval Augmented Generation: A Case Study in the Medical Domain (Ozaki et al., BioNLP 2025)
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https://preview.aclanthology.org/acl25-workshop-ingestion/2025.bionlp-1.1.pdf
Supplementarymaterial:
 2025.bionlp-1.1.SupplementaryMaterial.txt