Scarpati, S. E., Wells, C. S., Lewis, C., & Jirka, S. (2011). Accommodations and item-level analyses using mixture differential item functioning models . The Journal of Special Education , 45 (1), 54–62. https://doi.org/10.1177/0022466909350224

Accommodations studied were calculator, and several item presentation accommodations (including familiar administrator, noise buffer, magnification/overlay, clarify directions, large print, braille, place marker, track test items, amplification, read aloud items, sign interpret items, and electronic text reader).

Participants were over 73,000 students in grade 8 who participated in a statewide mathematics assessment in an unspecified state (U.S.). Approximately 17% were students with disabilities.

Statewide mathematics assessment scores, examined as an extant data set, served as the dependent variable.

Fourteen out of 34 items exhibited differential item functioning (DIF) when comparing scores of examinees with disabilities who used a calculator and students with disabilities who did not have any accommodations. Of these items, eight were easier for the accommodated group, and six were easier for the nonaccommodated group. Nine out of the 34 items exhibited DIF between examinees who had an item presentation accommodation and those who did not have any accommodations. Of these items, five were easier for the accommodated group and four were easier for the nonaccommodated group. Results also revealed that item difficulty and student ability level contribute to differences in performance above and beyond accommodation status.