Bolt, S. E., & Ysseldyke, J. (2008). Accommodating students with disabilities in large-scale testing: A comparison of differential item functioning (DIF) identified across disability types . Journal of Psychoeducational Assessment , 26 (2), 121–138. https://doi.org/10.1177/0734282907307703

Various accommodations were offered naturalistically and in various combinations in this extant data set—including individual/small group administration, extended-time, oral administration, dictated response, signing, large print, calculator/abacus, and braille. The focus of was an examination of measurement comparability for two groups of accommodated students with disabilities (i.e., accommodated students with physical disabilities and accommodated students with intellectual disabilities). Item-level characteristics of the test for these groups were systematically compared with those for a reference group of non-accommodated students without disabilities.

Almost 38,000 student scores from grades 4 and 8 in an unidentified state data set (U.S.) were examined. All but 2,000 were students with disabilities; that is, 1,000 students without disabilities in each grade served as a reference group.

Extant data were analyzed from three consecutive annual administrations of an unspecified state assessment in math.

A relatively large number of items with moderate to large differential item functioning (DIF) were identified for both accommodated disability groups, and significantly fewer items with DIF for the students without disabilities group. Put another way, students with disabilities using various accommodations were taking an academically different assessment than the students without disabilities not using accommodations.