A Critical Evaluation of Evaluations for Long-form Question Answering
Fangyuan Xu Yixiao Song Mohit Iyyer Eunsol Choi
Long-form question answering (LFQA) enables answering a wide range of
questions, but its flexibility poses enormous challenges for evaluation. We
perform the first targeted study of the evaluation of long-form answers,
covering both human and automatic evaluation practices. We hire domain experts
in seven areas to provide preference judgments over pairs of answers, along
with free-form justifications for their choices. We present a careful analysis
of experts' evaluation, which focuses on new aspects such as the
comprehensiveness of the answer. Next, we examine automatic text generation
metrics, finding that no existing metrics are predictive of human preference
judgments. However, some metrics correlate with fine-grained aspects of answers
(e.g., coherence). We encourage future work to move away from a single "overall
score" of the answer and adopt a multi-faceted evaluation, targeting aspects
such as factuality and completeness. We publicly release all of our annotations
and code to spur future work into LFQA evaluation.