The Impact of Homogeneity of Answer Choices on Item Difficulty and Discrimination

This study explored the impact of homogeneity of answer choices on item difficulty and discrimination. Twenty-two matched pairs of elementary and secondary mathematics items were administered to randomly equivalent samples of students. Each item pair comparison was treated as a separate study with the set of effect sizes analyzed using meta-analysis and a moderator analysis. The results show that multiple-choice (MC) items with homogeneous answer choices tend to be easier than MC items with nonhomogeneous answer choices, but the magnitude was related to item content (algebra vs. geometry) and answer choice construction strategy. For algebra items, items with homogeneous answer choices are easier than those with nonhomogeneous answer choices. However, the difficulty of geometry items with homogeneous and nonhomogeneous is not statistically different. Taking into account answer choice construction strategy, the findings showed that items with homogeneous answer choices were easier than items with nonhomogeneous answer choices when different strategy was applied. However, the same construction strategy was applied; thus, the difficulty of items with homogeneous answer choices and nonhomogeneous answer choices was not statistically different. In addition, we found that item discrimination does not significantly change across MC items with homogeneous and nonhomogeneous answer choices.