Evaluating LLM Autograders Without Ground Truth

Huijun Mao, Christopher J Piech


Abstract
LLM autograders are usually evaluated against human “ground truth,” a single reference label provided by one annotator or constructed by aggregating multiple annotations. However, human grading is often variable and subjective. We instead propose to evaluate LLM graders by treating humans and LLMs as two grading systems and characterize their agreement and disagreement. We operationalize this approach using distance correlation and generalizability theory. Across two programming-grading datasets, we find higher Human–LLM agreement on more objectively specified rubric items. On items involving greater subjective judgment, LLMs exhibit strong internal consensus, diverging more from human graders.
Anthology ID:
2026.emnlp-main.2465
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
55976–55986
Language:
URL:
https://aclanthology.org/2026.emnlp-main.2465/
DOI:
Bibkey:
Cite (ACL):
Huijun Mao and Christopher J Piech. 2026. Evaluating LLM Autograders Without Ground Truth. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 55976–55986, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Evaluating LLM Autograders Without Ground Truth (Mao & Piech, EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.2465.pdf