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International assessment: A Rasch model and teachers' evaluation of TIMSS science achievement items

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Abstract

The Trends in International Mathematics and Science Study (TIMSS) is a comparative assessment of the achievement of students in many countries. In the present study, a rigorous independent evaluation was conducted of a representative sample of TIMSS science test items because item quality influences the validity of the scores used to inform educational policy in those countries. The items had been administered internationally to 16,009 students in their eighth year of formal schooling. The evaluation had three components. First, the Rasch model, which emphasizes high quality items, was used to evaluate the items psychometrically. Second, readability and vocabulary analyses were used to evaluate the wording of the items to ensure they were comprehensible to the students. And third, item development guidelines were used by a focus group of science teachers to evaluate the items in light of the TIMSS assessment framework, which specified the format, content, and cognitive domains of the items. The evaluation components indicated that the majority of the items were of high quality, thereby contributing to the validity of TIMSS scores. These items had good psychometric characteristics, readability, vocabulary, and compliance with the assessment framework. Overall, the items tended to be difficult: constructed response items assessing reasoning or application were the most difficult, and multiple choice items assessing knowledge or application were less difficult. The teachers revised some of the sampled items to improve their clarity of content, conciseness of wording, and fit with format specifications. For TIMSS, the findings imply that some of the non-sampled items may need revision, too. For researchers and teachers, the findings imply that the TIMSS science items and the Rasch model are valuable resources for assessing the achievement of students. © 2012 Wiley Periodicals, Inc. J Res Sci Teach 49: 1321–1344, 2012

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