This article reports on a study that investigated the extent to which lexical frequency and lexical diversity contribute to writing proficiency scores on monolingual English-speaking writers’ and advanced multilingual writers’ academic compositions. The data consist of essays composed by 104 multilingual English learners enrolled in advanced second language writing courses at various intensive English programs and 68 monolingual English-speaking university students in a first-year composition course. Three independent raters evaluated the essays according to the TOEFL iBT independent writing rubric. Results from a binary logistic regression reveal that lexical diversity has a significantly greater impact on writing score than lexical frequency. Post hoc analyses show that lexical frequency has only a moderate relationship to lexical diversity, suggesting that diversity of mid-frequency vocabulary may be more important to writing proficiency than the use of more sophisticated terms that occur less frequently in natural language. Implications for practice suggest that it is not enough to simply teach vocabulary words in the second language composition classroom, but also to guide learners in how to employ these words in a varied manner in their writing.

中文翻译：

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词汇多样性对大学水平写作的贡献

本文报告了一项研究，该研究调查了词汇频率和词汇多样性对单语英语作家和高级多语种作家的学术作文写作能力分数的影响程度。数据包括由 104 名参加了各种强化英语课程的高级第二语言写作课程的多语种英语学习者和 68 名参加一年级作文课程的单语英语大学生撰写的论文。三位独立评分员根据 TOEFL iBT 独立写作评分标准对论文进行评估。二元逻辑回归的结果表明，词汇多样性对写作分数的影响比词汇频率要大得多。事后分析表明词汇频率与词汇多样性只有中等关系，表明中频词汇的多样性对写作能力可能比使用自然语言中出现频率较低的更复杂术语更重要。实践启示表明，在第二语言作文课堂中仅仅教授词汇是不够的，还要指导学习者如何在写作中以不同的方式使用这些词汇。