arXiv Computation and Language By Mateusz Modrzejewski, Tomasz Radzikowski

Poolwise: Evaluating Reward Models for Selection across Prompts

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Poolwise is a protocol that evaluates reward models for selecting training data across different prompts by choosing a fixed fraction of responses based on score and measuring the quality of the selected set with external labels. It reports within‑prompt ranking separately and shows that training each prompt’s mean score to match its average response rating improves selection over permuted or omitted mean targets in all tested seeds at 30% retention. In grouped HelpSteer experiments, the model with the highest within‑prompt accuracy selects a lower‑rated set than the correct‑mean model, and subtracting prompt means from reference responses preserves local rankings but reduces selected helpfulness for several reward models and judges. whyItMatters":"Poolwise offers a direct method to compare reward models and score transformations for data selection, addressing the limitation of existing benchmarks that only compare responses within the same prompt."

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