Position: Don't Use the CLT in LLM Evals With Fewer Than a Few Hundred Datapoints

Fuente: arXiv
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Autores principales: Bowyer, Sam, Aitchison, Laurence, Ivanova, Desi R.
Formato: Preprint
Publicado: 2025
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author Bowyer, Sam
Aitchison, Laurence
Ivanova, Desi R.
author_facet Bowyer, Sam
Aitchison, Laurence
Ivanova, Desi R.
contents Rigorous statistical evaluations of large language models (LLMs), including valid error bars and significance testing, are essential for meaningful and reliable performance assessment. Currently, when such statistical measures are reported, they typically rely on the Central Limit Theorem (CLT). In this position paper, we argue that while CLT-based methods for uncertainty quantification are appropriate when benchmarks consist of thousands of examples, they fail to provide adequate uncertainty estimates for LLM evaluations that rely on smaller, highly specialized benchmarks. In these small-data settings, we demonstrate that CLT-based methods perform very poorly, usually dramatically underestimating uncertainty (i.e. producing error bars that are too small). We give recommendations for alternative frequentist and Bayesian methods that are both easy to implement and more appropriate in these increasingly common scenarios. We provide a simple Python library for these Bayesian methods at https://github.com/sambowyer/bayes_evals .
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id arxiv_https___arxiv_org_abs_2503_01747
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Position: Don't Use the CLT in LLM Evals With Fewer Than a Few Hundred Datapoints
Bowyer, Sam
Aitchison, Laurence
Ivanova, Desi R.
Artificial Intelligence
Machine Learning
Rigorous statistical evaluations of large language models (LLMs), including valid error bars and significance testing, are essential for meaningful and reliable performance assessment. Currently, when such statistical measures are reported, they typically rely on the Central Limit Theorem (CLT). In this position paper, we argue that while CLT-based methods for uncertainty quantification are appropriate when benchmarks consist of thousands of examples, they fail to provide adequate uncertainty estimates for LLM evaluations that rely on smaller, highly specialized benchmarks. In these small-data settings, we demonstrate that CLT-based methods perform very poorly, usually dramatically underestimating uncertainty (i.e. producing error bars that are too small). We give recommendations for alternative frequentist and Bayesian methods that are both easy to implement and more appropriate in these increasingly common scenarios. We provide a simple Python library for these Bayesian methods at https://github.com/sambowyer/bayes_evals .
title Position: Don't Use the CLT in LLM Evals With Fewer Than a Few Hundred Datapoints
topic Artificial Intelligence
Machine Learning
url https://arxiv.org/abs/2503.01747