LexArabic: A receptive vocabulary size test to estimate Arabic proficiency

Arabic is understudied in second-language research (L2) and lacks rapid and adequate tools for measuring proficiency. Drawing inspiration from LexTALE and its extensions, this study created and validated a quick receptive vocabulary size test to estimate L2 Arabic proficiency. In Experiment 1, the initial version of LexArabic was designed and evaluated with 192 L1 and L2 speakers. Item analysis using point-biserial correlations and item response theory (IRT) was conducted to refine the test, resulting in a final version with 90 items (60 words, 30 nonwords). Experiment 2 assessed LexArabic reliability, validity, and accuracy using a new group of 260 L1 and L2 speakers. The validity of LexArabic was evaluated through objective tasks (a general Arabic proficiency test, L1 to L2 translation task, L2 to L1 translation task) as well as subjective tasks (self-rated proficiency). Results showed that LexArabic demonstrated good reliability (α > 90), validity (correlation with two objective tasks and one subjective task), as well as accuracy (AUC value = .88). The introduction of LexArabic has the potential to facilitate experimental research on both L1 and L2 Arabic speakers and contributes to the development of standardized L2 proficiency assessment across languages.