Abstract
The main goal of the present study is to answer the question of whether the lexical level of the reading section of the TOEFL Internet-based Test (TOEFL iBT) is beyond the vocabulary level of Japanese senior high school graduates. The lexical level was measured in terms of text coverage. The present study builds upon Chujo and Oghigian’s study. The notable difference in methodology compared to earlier text coverage studies on the TOEFL is an examination of real past TOEFL iBTs. Two objectives are explored in the present study. First, this study aims to examine how well a vocabulary of 3,000 word families, which is the lexical size target for Japanese high school graduates set by the Ministry of Education, Culture, Sports, Science, and Technology, enables students to comprehend reading passages in the TOEFL iBT. Second, it estimates a vocabulary size required to reach 95% and 98% coverage of these passages. Results showed that the most frequent 3,000 word families plus proper nouns as well as words that are defined in context yielded an average text coverage of 88.5% and that 6,000 word families plus proper nouns and defined words accounted for 95% of the text, and around 10,000 word families 98%. The findings suggest that Japanese high school graduates with a vocabulary of 3,000 word families would be expected to comprehend nearly 50% of reading passages in the TOEFL iBT and that learning a vocabulary beyond the 10,000-word frequency level may not be necessary unless 98% or more text coverage is required.

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