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Ziliang Samuel Zhong
New York University, NY, USA
Computer Science & IT

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Evidence-Calibrated RAG for Unanswerable Question Answering: Retrieval Coverage, Abstention Calibration, and Hallucination-Proxy Analysis on SQuAD 2.0 Ziliang Samuel Zhong; Jing Chen; Eric Zhong; Xinzhuo Sun
Journal of Technology Informatics and Engineering Vol. 4 No. 2 (2025): AUGUST | JTIE : Journal of Technology Informatics and Engineering
Publisher : University of Science and Computer Technology

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.51903/jtie.v4i2.536

Abstract

This paper presents a controlled and reproducible empirical study of evidence-calibrated retrieval-augmented question answering (RAG) for answerable and unanswerable reading-comprehension tasks using the SQuAD 2.0 benchmark. The study focuses on whether a system should abstain when retrieved evidence is insufficient rather than always producing an answer. Six lightweight architectures were evaluated on the full validation set of 11,873 questions, including closed-book, BM25, dense, hybrid, reranked, and a proposed evidence-calibrated hybrid RAG model. The proposed approach combines hybrid top-25 retrieval, lexical reranking, deterministic extractive answering, and evidence sufficiency calibration trained on 43,482 examples. On the validation set, it achieved 31.65% exact match, 34.74% F1, 53.01% answerability accuracy, 53.71% refusal F1, and a 37.49% hallucination-proxy rate. Although overall QA performance remains modest, calibrated evidence sufficiency substantially reduced unsupported answers compared with a forced-answer hybrid reranker, lowering the hallucination-proxy rate from 77.80% while improving F1. However, evidence calibration itself remained weak (AUROC 0.5475, ECE 0.1144). The findings demonstrate that retrieval coverage alone is insufficient to prevent hallucinations and highlight the need for stronger evidence calibration in trustworthy RAG systems.
Trajectory Reliability Prediction for Generalist AI Agents: Tool-Use Failure Analysis and Success Forecasting on ZClawBench Ziliang Samuel Zhong; Chenyu Li; Hengning Rao
Journal of Technology Informatics and Engineering Vol. 5 No. 1 (2026): APRIL | JTIE : Journal of Technology Informatics and Engineering
Publisher : University of Science and Computer Technology

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.51903/jtie.v5i1.539

Abstract

Generalist AI agents increasingly perform complex tasks through planning, tool execution, action revision, and artifact generation rather than isolated response generation. This study empirically investigates trajectory reliability prediction on ZClawBench, a public OpenClaw-style agent benchmark containing 696 model-task trajectories across 116 tasks, six model families, and six scenario categories. The study evaluates whether operational trajectory signals—including tool-call volume, replanning behavior, tool errors, invalid-action ratio, recovery patterns, looping indicators, trajectory length, and task category—can predict task success before manual evaluation. Since the dataset provides trajectories and identifiers but lacks explicit per-instance success labels, the binary target is reconstructed from official model-by-category score distributions and treated as a modeling assumption. Five-fold cross-validation with task-level splitting was applied to prevent task leakage. Logistic Regression, Random Forest, XGBoost, sequence TF-IDF classification, and a rubric-based trajectory judge were compared. Logistic Regression achieved the strongest calibrated performance, obtaining ROC-AUC of 0.970, F1-score of 0.913, Brier score of 0.066, and expected calibration error of 0.018. Feature analysis indicated that task difficulty, no-progress behavior, response size, tool errors, and invalid actions contributed most to reliability prediction. The findings suggest that lightweight trajectory diagnostics can support agent monitoring, failure triage, and routing decisions, while further validation with direct case-level evaluation labels is required for deployment claims.
Co-Authors Chenyu Li Eric Zhong Hengning Rao Jing Chen Xinzhuo Sun