Conditional Evaluation of Language Models with Cheap Auxiliary Signals
Organizations: Department of Statistics and Data Science, University of California, Los Angeles · Department of Statistics and Finance, School of Management, University of Science and Technology of China · Microsoft · Department of Statistics and Data Science, National University of Singapore
Abstract
Aggregate accuracy hides where models succeed and fail. Estimating conditional performance profiles from gold labels alone is expensive, while cheap auxiliary signals such as LLM-judge scores, pairwise comparisons, confidence scores, and judge-disagreement features can be collected for every benchmark item but are often biased or miscalibrated. We propose LACE (Local Augmented Control-Variate Evaluation), a semi-supervised estimator for conditional LLM evaluation. The key step is local centering: after subtracting the conditional mean of a cheap signal within the target profile region, any linear augmentation has zero conditional mean and therefore cannot change the estimand. The augmentation coefficient is used only for efficiency, and a local ridge control variate combines a gold-label residual mean from the labeled subset with a cheap-signal mean from the full item pool. We prove calibration-free identification, unbiasedness for grouped profiles, local oracle optimality within centered linear augmentations, and first-order adaptivity to the estimated coefficient. The resulting gain formula is governed by a population local , which characterizes how the efficiency attainable from the cheap signals varies across profile values. We also derive corresponding estimators for direct paired model gaps and deployment-weighted scores. We empirically evaluate the primary performance-profile estimator on MATH-500, ScienceQA, MMLU, WinoGrande, HellaSwag, TruthfulQA, GSM8K, and ARC.
Figures & tables
| Benchmark | Profiling axis | Domain | |
|---|---|---|---|
| MATH-500 | difficulty level ( ) | 500 | math reasoning |
| ScienceQA | grade level ( ) | 500 | science (text-only) |
| MMLU | question token length | 500 | general knowledge |
| WinoGrande | sentence length (tokens) | 500 | commonsense |
| HellaSwag | context sentence length | 500 | commonsense |
| TruthfulQA | question token length | 500 | factuality |
| Estimator | Overall | |||
|---|---|---|---|---|
| Naive | ||||
| Plug-in (judge) | ||||
| Plug-in (multi) | ||||
| Aug. plug-in | ||||
| Global CV | ||||
| Per-signal CV |
Appendix figures & tables36 assets
Supplementary material from the paper’s appendix.
Appendix
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| Method | Opus 4.6 judge + anchor | Llama-3.1-8B judge + anchor | GPT-OSS-20B judge + anchor |
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| Benchmark / candidate | Jittered Gaussian | Triangular ordinal | Within group |
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| MATH-500 / Claude Haiku 3 | 6.14/5.78/6.07 | 4.82/4.38/4.41 | 1.75/3.73/7.27 |
| MATH-500 / Ministral 3B | 4.19/4.73/5.20 | 2.84/3.72/4.16 | 1.36/1.76/3.23 |
| MATH-500 / Qwen3 32B | 5.47/5.38/4.32 | 3.27/3.99/3.17 | 2.10/3.35/3.63 |
| ScienceQA / Claude Haiku 3 | 5.96/5.70/5.13 | 1.47/2.00/2.99 | 0.65/1.05/1.72 |
| ScienceQA / Ministral 3B | 5.72/6.56/5.67 | 1.78/2.72/3.14 | 0.61/0.70/1.59 |
| ScienceQA / Qwen3 32B | 5.71/5.90/5.12 | 1.22/2.49/2.70 | 0.34/0.52/1.45 |
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| Plug-in (multivariate) | ( ) | ( ) | ( ) |
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| Label fraction | Theorem 4 prediction | Empirical RE (oracle) ( CI) | Empirical RE (feasible) ( CI) | Empirical RE (oracle) fixed ( CI) |
|---|---|---|---|---|
| 0.05 | 3.245 | 3.216 | 3.159 | 2.332 |
| 0.10 | 2.902 | 2.916 | 2.904 | 2.197 |
| 0.15 | 2.625 | 2.610 | 2.601 | 1.994 |
| Method | RE | RE | RE | Overall | Best |
|---|---|---|---|---|---|
| Naive | 0/72 | ||||
| LACE | 72/72 | ||||
| Global CV | 0/72 | ||||
| Per-signal CV | 0/72 | ||||
| Residual-only | 0/72 | ||||
| Plug-in (judge) | 0/72 |
| Signal | Description | API calls | Range |
|---|---|---|---|
| Mean of 3 pointwise judge scores | 3 | ||
| Variance of 3 pointwise judge scores | 0 (derived) | ||
| Pairwise vs. weak anchor (Ministral 3B) | 2 | ||
| Pairwise vs. medium anchor (Haiku 3) | 2 | ||
| Pairwise vs. strong anchor (Opus 4.6) | 2 | ||
| Self-reported confidence | 0 additional |
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