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confidence estimation

Confidence estimation is the process of measuring and quantifying how certain an artificial intelligence or machine learning model is regarding the correctness, accuracy, or factuality of its own predictions and outputs. In natural language processing and automated decision-making, it assigns numerical scores or calibrated probabilities to generated answers, classifications, or factual statements to help distinguish dependable results from potential errors and hallucinations. These estimates can be derived through diverse methods, including analyzing output probability distributions, probing internal model states, prompting models to articulate their certainty, or measuring consistency across varying inputs and generations. Reliable confidence estimation is essential for error detection, selective prediction, and model calibration, enabling systems to signal when outputs can be trusted safely or when human intervention is required.

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Factual Confidence of LLMs: on Reliability and Robustness of Current Estimators

Factual Confidence of LLMs: on Reliability and Robustness of Current Estimators

Matéo Mahaut, Laura Aina, Paula Czarnowska, Momchil Hardalov, Thomas Müller, Lluís Màrquez

OrganizationsAmazon Web ServicesUniversitat Pompeu Fabra

Why you should read this

Evaluates five major families of factual confidence estimators across multiple large language models and tasks, revealing that internal hidden-state probes achieve superior reliability while exposing how easily model confidence fluctuates across semantically equivalent prompts.

Large Language Models (LLMs) tend to be unreliable in the factuality of their answers. To address this problem, NLP researchers have proposed a range of techniques to estimate LLM’s confidence over facts. However, due to the lack of a systematic comparison, it is not clear how the different methods compare to one another. To fill this gap, we present a survey and empirical comparison of estimators of factual confidence. We define an experimental framework allowing for fair comparison, covering both fact-verification and question answering. Our experiments across a series of LLMs indicate that trained hidden-state probes provide the most reliable confidence estimates, albeit at the expense of requiring access to weights and training data. We also conduct a deeper assessment of factual confidence by measuring the consistency of model behavior under meaning-preserving variations in the input. We find that the confidence of LLMs is often unstable across semantically equivalent inputs, suggesting that there is much room for improvement of the stability of models’ parametric knowledge. Our code is available at https://github.com/amazon-science/factual-confidence-of-llms.

Added

2026-10-03