The purpose of this study was to develop the ability estimation method considering different item
weighting in multiple choice items. In order to accomplish the purpose, this study suggested the new
estimation method by adjusting the location parameters of boundary characteristic curves under the graded
response model. The results showed that the correlation between the raw-scores and the estimated s by
the new estimation method considering item weighting was higher than the correlation between raw-score
ranking and the estimated s by traditional IRT approach. In addition, compared with raw-score ranking,
there existed less changes of ranking when applying the new ability parameter estimation method. As a
result, the method proposed in this study might be considered as an effective alternative in the situation
where the differential item weights were adopted for multiple choice items.