FactTest: Factuality Testing in Large Language Models with Finite-Sample and Distribution-Free Guarantees

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Main Authors: Nie, Fan, Hou, Xiaotian, Lin, Shuhang, Zou, James, Yao, Huaxiu, Zhang, Linjun
Format: Preprint
Published: 2024
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author Nie, Fan
Hou, Xiaotian
Lin, Shuhang
Zou, James
Yao, Huaxiu
Zhang, Linjun
author_facet Nie, Fan
Hou, Xiaotian
Lin, Shuhang
Zou, James
Yao, Huaxiu
Zhang, Linjun
contents The propensity of Large Language Models (LLMs) to generate hallucinations and non-factual content undermines their reliability in high-stakes domains, where rigorous control over Type I errors (the conditional probability of incorrectly classifying hallucinations as truthful content) is essential. Despite its importance, formal verification of LLM factuality with such guarantees remains largely unexplored. In this paper, we introduce FactTest, a novel framework that statistically assesses whether a LLM can confidently provide correct answers to given questions with high-probability correctness guarantees. We formulate factuality testing as hypothesis testing problem to enforce an upper bound of Type I errors at user-specified significance levels. Notably, we prove that our framework also ensures strong Type II error control under mild conditions and can be extended to maintain its effectiveness when covariate shifts exist. Our approach is distribution-free and works for any number of human-annotated samples. It is model-agnostic and applies to any black-box or white-box LM. Extensive experiments on question-answering (QA) and multiple-choice benchmarks demonstrate that FactTest effectively detects hallucinations and improves the model's ability to abstain from answering unknown questions, leading to an over 40% accuracy improvement.
format Preprint
id arxiv_https___arxiv_org_abs_2411_02603
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle FactTest: Factuality Testing in Large Language Models with Finite-Sample and Distribution-Free Guarantees
Nie, Fan
Hou, Xiaotian
Lin, Shuhang
Zou, James
Yao, Huaxiu
Zhang, Linjun
Computation and Language
Artificial Intelligence
Machine Learning
The propensity of Large Language Models (LLMs) to generate hallucinations and non-factual content undermines their reliability in high-stakes domains, where rigorous control over Type I errors (the conditional probability of incorrectly classifying hallucinations as truthful content) is essential. Despite its importance, formal verification of LLM factuality with such guarantees remains largely unexplored. In this paper, we introduce FactTest, a novel framework that statistically assesses whether a LLM can confidently provide correct answers to given questions with high-probability correctness guarantees. We formulate factuality testing as hypothesis testing problem to enforce an upper bound of Type I errors at user-specified significance levels. Notably, we prove that our framework also ensures strong Type II error control under mild conditions and can be extended to maintain its effectiveness when covariate shifts exist. Our approach is distribution-free and works for any number of human-annotated samples. It is model-agnostic and applies to any black-box or white-box LM. Extensive experiments on question-answering (QA) and multiple-choice benchmarks demonstrate that FactTest effectively detects hallucinations and improves the model's ability to abstain from answering unknown questions, leading to an over 40% accuracy improvement.
title FactTest: Factuality Testing in Large Language Models with Finite-Sample and Distribution-Free Guarantees
topic Computation and Language
Artificial Intelligence
Machine Learning
url https://arxiv.org/abs/2411.02603