arXiv Machine Learning

How Sensitive Are LLM Leaderboard Claims to Hidden Model Selection?

The paper investigates how many hidden model variants can exist while still supporting a published leaderboard margin that shows a provider’s advantage over a fixed comparator. It derives a sensitivity curve for a fixed candidate family under a Gaussian margin model, linking the maximum number of hidden variants to a lower bound on within‑family correlation. Using this framework, an audit of 394 adjacent‑rank claims on the Open LLM Leaderboard found that 391 lack statistical support before any correction, and that certification of the remaining claims depends on assumptions about the hidden family’s correlation.

arXiv Machine Learning
Sep 2

Are Near-Tied LLM Rankings Robust to Family-DIF-Guided Benchmark Recomposition?

The study investigates whether small differences in leaderboard rankings between large language models (LLMs) are robust to changes in benchmark composition. Using item‑level responses from five benchmarks and a spectral approximation to multidimensional item‑response theory, the authors find that while overall rankings remain highly correlated, a significant portion (30.9–47.1%) of near‑tie pairs reverse order when benchmark items are recomposed based on low differential item functioning. This suggests that sub‑one‑percentage‑point leaderboard gaps may not reliably reflect true model superiority.

By Qiaoyuan Zheng, Yiqu Yang
arXiv Computation and Language
Sep 4

Contamination Inflates Scores but Rarely Reorders Large Language Model Leaderboards

The paper investigates how benchmark contamination—leakage of test items into training data—affects large language model (LLM) leaderboards. By comparing original test items with semantically equivalent paraphrases, the authors measure contamination as a violation of anchor-item invariance and find that it inflates absolute scores but rarely changes model rankings. Across 47 public models and 74 finetuned models on four benchmarks, the rank correlation between standard and paraphrase-controlled leaderboards is 0.997, with only a handful of cases showing differential contamination that could alter rankings.

By Xingyao Xiao (Stanford University), Yihong Cheng (City University of Macau)
arXiv AI
6d ago

Accounting for Bias Enables Sustainable LLM Evaluation

The paper argues that the current LLM-as-a-judge evaluation method, which compensates for systematic measurement bias by increasing the number of comparisons, is statistically unsound and computationally wasteful. It identifies that treating LLM judges as neutral ignores documented biases such as position bias, verbosity bias, judge severity, and self‑enhancement. The authors propose a unified latent variable framework that jointly models pairwise and ordinal data while explicitly correcting for these confounders, enabling reliable rankings with far fewer comparisons and negligible additional compute.

By Harshita Katoch, David Antony Selby, Gerrit Gro{\ss}mann, Sebastian Vollmer
arXiv AI
Sep 24

Ask Which, Not How Good: Sizing Benchmarks Scored by an LLM

The study analyzes 373,019 judgments from LLM‑scored benchmarks, decomposing variance into system, item, judge, and interaction components via generalizability theory. It finds that with a single judge, generalizability converges to a ceiling determined by the system‑by‑judge variance, which is substantially lower in pairwise preference settings, allowing one judge to suffice. The research also reveals significant biases in presentation order and highlights that many published win‑rate claims fall below the measured floor of the benchmarks.

By Atul Anand
arXiv AI
Sep 25

How Reproducible Are Evaluation Conclusions? A Self-Audit of LLM-Inferred Prompt Structure

The paper investigates the reliability of ranking tables produced by small-sample evaluations of large language models (LLMs). Using LLM‑inferred prompt structure across eight model variants, the authors find that prompt‑structure recovery is highly unstable, with only the bottom of the ranking consistently reproducible. They demonstrate that standard evaluation practices can misrepresent model performance and propose reporting practices to improve transparency.

By Dipankar Sarkar
arXiv Computation and Language
Sep 16

Bias Audits Detect Bias but Disagree on Ranking: Evidence from Ten Instruments and Ten Frontier Models

The study evaluates ten bias audit instruments across ten advanced language models on occupational gender, age, and socioeconomic status. While each tool reliably detects bias, their rankings of model performance are essentially random, indicating that different audits measure distinct constructs. The findings show that a single audit can identify bias direction within its own framework, but no audit can consistently rank models against one another.

By William Guey, Pierrick Bougault, Wei Zhang, Vitor D. de Moura, Jos\'e O. Gomes