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Automated Evaluation of Retrieval-Augmented Language Models with Task-Specific Exam Generation
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Proposes automatically generating task-specific multiple-choice exams from a RAG corpus and scoring RAG pipelines with a hierarchical Item Response Theory model, showing retrieval choice can matter more than LLM size.
Problem
Evaluating Retrieval-Augmented LLM (RAG) pipelines on narrow, domain-specific tasks lacks an automated, interpretable, and cost-efficient method, since public benchmarks and existing RAG metrics do not capture task-specific factual accuracy.
Approach
An LLM generates multiple-choice exams from the task's document corpus, filtered by NLP-based a-priori checks; RAG pipelines are scored by answering the exam, and a hierarchical IRT model decomposes ability into LLM, retriever, and in-context-learning components, with item information used to iteratively prune uninformative questions.
Key results
- Best absolute accuracy on t_ops with LlamaV2-70B and BM25 or MultiQA reaches about 71-73%, versus 63% for Oracle-free retrieval gaps shown in the table (e.g. ClosedB 63.0%).
- IRT analysis on t_sec: switching from SIAM to DPRV2 yields a larger ability gain (about 1.61 logits) than switching from Mistral-7B to LlamaV2-70B (about 0.66), supporting retrieval choice over model size.
- Averaged over tasks, LlamaV2-70B with DPRV2 reaches 71.8% accuracy vs 49.3% for closed-book LlamaV2-70B.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| Use a hybrid retriever instead of a dense-only or sparse-only retriever | RAG pipelines across the evaluated tasks · AWS DevOps, StackExchange, Arxiv, and SEC Filings | accuracy | Mixed |
| Use BM25 rather than dense retrieval | RAG pipelines on tasks with easily identifiable terms · SEC Filings and Arxiv | accuracy | Helped |
| Switch retrieval from SIAM to DPRV2 | RAG pipelines · SEC Filings | ability | Helped |
| Use SIAM retrieval rather than no retrieval | RAG pipelines · AWS DevOps and SEC Filings | accuracy | Hurt |
| Scale the LLM while using no retrieval | RAG pipelines · Evaluated tasks | accuracy | Mixed |
| Iteratively discard questions based on inferred discrimination | Generated exams · Arxiv, AWS DevOps, and StackExchange | informativeness | Helped |
| Iteratively discard questions based on inferred discrimination | Generated exams · SEC Filings | informativeness | Mixed |
Surprising findings
- A poorly aligned retriever (SIAM) can yield worse accuracy than no retrieval at all (ClosedB), e.g. on t_sec and t_ops.
- Oracle can be outperformed by some retrievers on t_arx, because multiple document chunks overlap in information.
Limitations
- Evaluation is limited to multiple-choice factual accuracy and does not measure all RAG dimensions such as faithfulness or coherence.
- Only three LLMs (Mistral-7B, LlamaV2-13B/70B), three ICL modes, and seven retrieval mechanisms were tested.
- Exam questions are generated by LlamaV2-70B itself, which may introduce generator bias.
Experimental setup
Datasets: AWS Knowledge Center webpages ArXiv abstracts StackExchange questions SEC filings
Benchmarks: DevOps (t_ops) Arxiv (t_arx) StackExchange (t_stk) SEC Filings (t_sec)
Metrics: accuracy IRT ability item information
Baselines: ClosedBook SIAM DPR BM25 MultiQA DPRV2 Oracle
Builds on: Item Response Theory BM25 Bloom's revised taxonomy
Closest papers by meaning
- Long-Context LLMs Meet RAG: Overcoming Challenges for Long Inputs in RAG (ICLR 2025 · similarity 0.89)
- Self-RAG: Learning to Retrieve, Generate, and Critique through Self-Reflection (ICLR 2024 · similarity 0.89)
- Benchmarking Large Language Models in Retrieval-Augmented Generation (AAAI 2024 · similarity 0.89)
- Speculative RAG: Enhancing Retrieval Augmented Generation through Drafting (ICLR 2025 · similarity 0.89)
- Retrieval is Not Enough: Enhancing RAG through Test-Time Critique and Optimization (NeurIPS 2025 · similarity 0.89)
- Cooperative Retrieval-Augmented Generation for Question Answering: Mutual Information Exchange and Ranking by Contrasting Layers (NeurIPS 2025 · similarity 0.88)
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