Validating a Multi-Dimensional Rating Scale for Lexical Proficiency in L2 Academic Speech: A Mixed-Methods Approach

This study aimed to develop and validate an analytical rating scale specifically designed to assess the lexical proficiency of Chinese college students in Academic English speaking tasks. A multi-layer construct of lexical proficiency was first developed and operationalized into an eight-dimension rating scale, including word diversity, word sophistication, word accuracy, and word fluency, phraseological diversity, phraseological sophistication, phraseological accuracy, and phraseological fluency. The reliability and validity of the scale were then examined by using the many-facet Rasch model and confirmatory factor analysis with 600 academic speech samples. The results showed that the rating scale could successfully and reliably differentiate levels of lexical proficiency among participants. High construct validity was confirmed with excellent model fit and support for the proposed dimensions. The proposed analytical rating scale provides a practical approach to comprehensively assessing lexical proficiency in academic speaking contexts. The study has implications for L2 vocabulary instruction, assessment, and speaking assessment in L2 academic contexts.