Effects of question formats on student and item performance

To determine the effect of 3 variations in test item format on item statistics and student performance.

Fifteen pairs of directly comparable test questions were written to adhere to (standard scale) or deviate from (nonstandard scale) 3 specific item-writing guidelines. Differences in item difficulty and discrimination were measured between the 2 scales as a whole and for each guideline individually. Student performance was also compared between the 2 scales.

The nonstandard scale was 12.7 points more difficult than the standard scale (p=0.03). The guideline to avoid "none of the above" was the only 1 of the 3 guidelines to demonstrate significance. Students scored 53.6% and 41.3% (p<0.001) of total points on the standard and nonstandard scales, respectively.

Nonstandard test items were more difficult for students to answer correctly than the standard test items, provided no enhanced ability to discriminate between higher- and lower-performing students, and resulted in poorer student performance. Item-writing guidelines should be considered during test construction.