Uncertainty Quantification for In-Context Learning of Large Language Models
Chen LingXujiang ZhaoXuchao ZhangWei ChengYanchi LiuYiyou SunMika OishiTakao OsakiKatsushi MatsudaJie Ji
Presents a Bayesian framework that decomposes predictive uncertainty in large language model in-context learning into prompt-induced aleatoric and model-induced epistemic components, enabling unsupervised diagnostic evaluation of output reliability across both white-box and black-box settings.
Large Language Models often produce unreliable outputs or hallucinations, posing significant operational and decision-making risks in practical applications. While prompting models with a few example demonstrations (in-context learning) improves performance, existing uncertainty metrics fail to distinguish whether model confusion stems from poor demonstration examples or limitations in the model itself.
The article aims to formulate and evaluate an unsupervised framework that quantifies and separates predictive uncertainty in in-context learning into two distinct sources: data-driven variation from the demonstrations and parameter-level variation from the model configurations.
The researchers evaluated this approach using natural language understanding benchmarks across sentiment analysis, topic classification, and linguistic acceptability. They tested open-source models, primarily LLaMA-2 (7B, 13B, and 70B parameter versions) and OPT-13B, across thousands of test cases. For accessible white-box models, the framework aggregates prediction entropy using beam search decoding across varying demonstration sets, while also defining a variance-based alternative for black-box systems.
The evaluation revealed several critical findings. First, decomposing uncertainty into data-level and model-level components identified misclassified samples more accurately than standard baseline metrics, such as semantic and raw token entropy. Second, ensuring demonstrations cover every label class consistently reduced error rates and uncertainty compared to purely random selection. Third, scaling up model capacity from 7B to 70B parameters significantly reduced overall uncertainty and improved error-detection accuracy. Finally, model-level uncertainty proved to be the most reliable indicator for detecting out-of-distribution or irrelevant prompt demonstrations, achieving area-under-the-curve scores exceeding 0.93.
These findings provide immediate practical value for managing generative AI risks. Organizations deploying language models can use these decomposed metrics as automated guardrails to reject low-confidence outputs, diagnose faulty prompt designs, and identify when queries fall outside the system's operational domain. Rather than treating uncertainty as a single uninterpretable number, teams can determine whether to fix prompt examples or upgrade the underlying model.
Stakeholders should implement balanced class-sampling strategies when designing few-shot prompts and integrate model-level uncertainty monitoring into production pipelines to catch out-of-domain inputs. Before deploying this approach on open-ended generation tasks like summarization or drafting, teams should run additional pilot tests, as the current framework relies on structured classification and closed-form outputs where specific answer tokens can be isolated.
Confidence in these findings is strong for deterministic natural language classification tasks across standard model architectures. However, decision-makers should remain cautious regarding open-ended text generation, where linguistic redundancy makes identifying core predictive tokens more challenging and requires further research.
- Paper: Aleatoric and epistemic uncertainty in machine learning: an introduction to concepts and methods, Eyke Hüllermeier et al. (2019). Its distinction between irreducible data uncertainty and model ignorance supplies the conceptual foundation for the source’s aleatoric–epistemic decomposition.
- Paper: A survey of uncertainty in deep neural networks, Jakob Gawlikowski et al. (2021). This survey explains how deep-learning methods separate data-driven from model-driven uncertainty, preparing you to understand the source’s decomposition and estimation choices.
- Paper: What Uncertainties Do We Need in Bayesian Deep Learning for Computer Vision?, Alex Kendall et al. (2017). Its Bayesian treatment of aleatoric and epistemic uncertainty provides an earlier applied framework for the two uncertainty sources the source measures.
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