A Study On Quality Of CET Multiple-choice Items-Item Response Theory Approach

Language testing emerges with the development of language teaching and the two are closely interrelated with each other —English language testing is an important approach used for evaluating the student's English ability and the teaching effects. Whether the evaluation is objective, accurate and appropriate for the students'ability level relies on the test quality. Classical test theory (CTT), the most used approach for test quality evaluation nowadays, has an obvious defect that the computation result fluctuates a lot with the change of the samples tested. Item response theory (IRT), the testing theory originated from the 1930s, has the superiority that the examinee's ability parameter is independent with the item parameters. But because of its complicated mathematical computations, many researchers of applied linguistics can only bemoan their inadequacy to apply this method. The characteristic of objective multiple-choice items directly influences the quality of a test, for it is a main test format in college English test, and thus it is necessary to make an all-round quality evaluation on them. Taking the multiple-choice items in a college English test paper for second semester final examination as the object, this study adopts IRT to make a comprehensive quality evaluation on the items and conducts an in-depth analysis of the factors leading to poor quality items. Two samples are drawn randomly from the population. The first sample consists of 207 examinees, used for comprehensive analysis; the second sample contains 200 examinees majoring in science and 200 in arts, used for checking biased items. The methods applied in data analysis are the analysis of item characteristic curve, item information function, test information function and item validity, as well as the checking of biased items. Item information function and test information function are the reliability indexes for individual items and the whole test respectively. The results of data analysis indicate that some items are of poor quality and the test reliability is not very high. Though the test has good face validity and content validity, its predictive validity is very low. The test does not contain biased items, which means the background knowledge concerning an examinee's major will not influence his performance. The factors leading to poor quality items fall into two categories, violation of the basic multiple-choice-item writing principles and the unique factors leading to poor...