Response Quality Assessment for Retrieval-Augmented Generation via Conditional Conformal Factuality

Existing research on Retrieval-Augmented Generation (RAG) primarily focuses on improving overall question-answering accuracy, often overlooking the quality of sub-claims within generated responses. Recent methods that attempt to improve RAG trustworthiness, such as auto-evaluation metrics, often lack probabilistic guarantees or requires ground truth answers, failing to provide reliable and scalable assessment. To address these limitations, we propose Conformal-RAG, a novel framework inspired by recent applications of conformal prediction in large language models (LLMs). Conformal-RAG leverages conformal prediction and internal information from the RAG mechanism to offer statistical guarantees on response quality. It ensures conditional coverage (potentially spanning multiple sub-domains) without requiring manual calibration of conformal sets, making it suitable for complex RAG applications. Compared to existing RAG auto-evaluation methods, Conformal-RAG offers statistical guarantees on the quality of refined sub-claims, ensuring response reliability without needing ground truth answers. Additionally, our experiments demonstrate that by leveraging RAG internal information, Conformal-RAG retains more high-quality sub-claims from the response while maintaining the same reliability guarantee as naïve adaptations of conformal prediction in LLMs. Specifically, Conformal-RAG retains 60% more high-quality sub-claims in biography generation tasks and 20% more in medication question-answering tasks.