Effects of item format on item discrimination and difficulty.

Studied the effects of item stem orientation (positive-negative), structure (open-closed), and inclusive alternatives on item difficulty and discrimination. Data were obtained from 1,124 undergraduates taking a regularly scheduled test. Results indicate that item difficulty was critically affected by all 3 independent variables with no interactions and that item discrimination was affected by the use of an inclusive alternative with a significant interaction between orientation and stem structure. Suggestions are made with respect to effective item-writing strategies. (PsycINFO Database Record (c) 2010 APA, all rights reserved)