Testing Vocabulary Size of Omani Undergraduates

This study investigates the reliability and validity of the XK-Lex a test of knowledge of the most frequent 10000 words in English by testing the vocabulary size of 42 Omani undergraduate students. The outcomes show good reliability and validity for the XK-Lex test. Comparing students’ scores on XK-Lex with those for another test; again a good correlation was found showing a good concurrent validity for the XK-Lex test. Parallel forms and split-half analyses were used to examine the reliability of the XK-Lex test the results suggesting high reliability. Concurrent validity construct validity and predictive validity were also considered in order to verify the validity of the XK-Lex. The conclusion to be drawn from this study is that the XK-Lex test can be used to estimate the vocabulary size of high and low level learners and that it could be used as a level progress diagnostic or placement test.