When Judgment Becomes Noise: How Design Failures in LLM Judge Benchmarks
  Silently Undermine Validity
Authors: name: Benjamin Feuer; name: Chiung-Yi Tseng; name: Astitwa Sarthak Lathe; name: Oussama Elachqar; name: John P Dickerson
Published: 2025-09-24 16:26:47

Abstract: LLM-judged benchmarks are increasingly used to evaluate complex model
behaviors, yet their design introduces failure modes absent in conventional
ground-truth based benchmarks. We argue that without tight objectives and
verifiable constructions, benchmark rankings can produce high-confidence
rankings that are in fact largely noise. We introduce two mechanisms to
diagnose these issues. Schematic adherence quantifies how much of a judge's
overall verdict is explained by the explicit evaluation schema, revealing
unexplained variance when judges deviate from their own rubric. Psychometric
validity aggregates internal consistency and discriminant validity signals to
quantify irreducible uncertainty in any benchmarking run. Applying these tools
to Arena-Hard Auto, we find severe schema incoherence and factor collapse
across popular judges: for example, unexplained variance exceeding 90 percent
for DeepSeek-R1-32B and factor correlations above 0.93 for most criteria. We
also show that the ELO-style aggregation used by Arena-Hard Auto collapses and
masks genuine ranking uncertainty. Our results highlight design failures that
undermine validity and offer actionable principles for building better-scoped,
reliability-aware LLM-judged benchmarks. We release our code at
https://anonymous.4open.science/r/judgment-to-noise-947D/README.md