Reliable but Design-Sensitive: Instrument Uncertainty in LLM Annotation

Thomas Reiter, Christoph Kern, Fedor Miasnikov, Sofiia Nikolenko, Rob Chew, Stephanie Eckman, Frauke Kreuter


Abstract
Large language models (LLMs) can give reliable labels under one setup yet change those labels when researchers make other reasonable design choices. We tested seven LLMs, 12 task designs, three independent runs, and 3,000 tweets labeled for offensive language and hate speech. Repeating the same model and task design produced high agreement (median Fleiss’ 𝜅 = 0.91). Agreement fell when we changed the task design for the same tweets (median Cohen’s 𝜅 = 0.76). Task design and model choice increased the variance of estimated prevalence by factors of 76.7 for offensive language and 110.6 for hate speech compared with sampling variance alone. Variation across LLM task designs reached 560–572 basis points, compared with 270–331 basis points across five human instrument versions. Confidence scores did not solve this problem. They tracked repeated model outputs more closely than agreement with human labels, and grouping six tweets in one prompt lowered mean offensive-language confidence by 660 basis points. We call the variation caused by task design and model choice instrument uncertainty. Researchers can measure it only by comparing reasonable task designs. Repeating one setup or relying on confidence scores cannot replace that test.
Anthology ID:
2026.uncertainlp-main.20
Volume:
The Proceedings of the Third Workshop on Uncertainty-Aware NLP
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Wilker Aziz, Jonathan Berant, Bryan Eikema, Evgenia Ilia, Marie-Catherine de Marneffe, Barbara Plank, Artem Shelmanov, Swabha Swayamdipta, Jörg Tiedemann, Artem Vazhentsev, Raúl Vázquez, Chrysoula Zerva
Venues:
UncertaiNLP | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
312–327
Language:
URL:
https://aclanthology.org/2026.uncertainlp-main.20/
DOI:
Bibkey:
Cite (ACL):
Thomas Reiter, Christoph Kern, Fedor Miasnikov, Sofiia Nikolenko, Rob Chew, Stephanie Eckman, and Frauke Kreuter. 2026. Reliable but Design-Sensitive: Instrument Uncertainty in LLM Annotation. In The Proceedings of the Third Workshop on Uncertainty-Aware NLP, pages 312–327, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Reliable but Design-Sensitive: Instrument Uncertainty in LLM Annotation (Reiter et al., UncertaiNLP 2026)
Copy Citation:
PDF:
https://aclanthology.org/2026.uncertainlp-main.20.pdf