The Effects of Reusing Written Test Items: A Study Using the Rasch Model

Background. Relevant literature reports no increase in individual scores when test items are reused, but information on change in item difficulty is lacking. Purpose. To test an approach for quantifying the effects of reusing items on item difficulty. Methods. A total of 671 students sat a newly introduced exam in four testing shifts. The test forms experimentally combined published, unused, and reused items. Figures quantifying reuse effects were obtained using the Rasch model to compare item difficulties from different person samples. Results. The observed decrease in mean item difficulty for reused items was insignificant. Students who self-scheduled to the last test performed worse than other students did. Conclusion. Availability of leaked material did not translate into higher individual scores, as mastering leaked material does not guarantee transfer of knowledge to new exam items. Exam quality will not automatically deteriorate when a low ratio of randomly selected items is reused.