Improving the function of multiple-choice items in the assessment of the skills necessary for the development of proportional reasoning

Using Rasch Measurement theory, this study confirmed that it is possible to create options in multiple-choice items which detect partial knowledge, and that the allocation of a partial score for the selection of such options adds to the information gathered about student learning. Both the awarding of partial credit, and the removal of responses that were likely to have been guessed, provided more precise measures of item difficulty and student proficiency. While the study focused on the assessment of proportional reasoning for early secondary students, the processes used can be applied in other populations and subject areas.