| Summary: | 碩士 === 國立臺灣師範大學 === 英語學系在職進修碩士班 === 102 === Vocabulary size is closely related to language learners’ overall proficiency. It correlates significantly with listening, speaking, reading and writing. Incorporating a word into one’s mental lexicon requires repetition. To acquire new vocabulary words effectively, a learner need to have a clear idea of his current vocabulary size to concentrate his efforts onto the reading and vocabulary learning material that fits his present vocabulary size. However, for now, no vocabulary size test is developed based on the Taiwanese learning context.
The present study is aimed to develop a vocabulary size test based on the 6,840 reference word list released by College Entrance Exam Center. The validity, reliability and test quality of the test in question are checked by the three-parameter logistic model of Latent Trait Theory. The test takes on the format of four-choice multiple choice questions, containing 180 items. The study also sets forth to explore the interaction between frequency levels and the difficulty, discrimination and pseudo-guessing parameters. Participants in this study are freshmen and sophomores from a senior high school in Taichung, totaling 1,838 subjects.
Findings revealed that the test in question exhibited satisfactory validity and reliability. Validity was supported by overall model fit and hierarchical difficulty along with the high reliability value (0.98). With validity and reliability established, the MC format was proven to be an appropriate format for vocabulary size test. Furthermore, it was found that the mean difficulty across frequency bands formed an upward nonlinear slope with the decrease of word frequency. The rise of difficulty from Level 1 to Level 3 was much steeper than that from Level 3 to Level 6. Such phenomenon revealed that the first three thousand words are the threshold for further vocabulary expansion. Once learners cross this threshold, they would be equipped with the ability to apply strategies such as extensive reading and word schema to acquire new words. On the other hand, it was found that lower-achievers are prone to take guesses and favor the distractors in the middle position. Content analysis suggests that clues in stems and distractors exert a certain influence on the discrimination power of items, which shows that learners are capable of transferring their word schema to unknown words.
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