Using Differential Item Functioning to Investigate the Impact of Testing Accommodations on an English-Language Arts Assessment for Students who are Blind or Visually Impaired

This validity study examined differential item functioning (DIF) results on large-scale state standards-based English-language arts assessments at grades 4 and 8 for students without disabilities taking the test under standard conditions and students who are blind or visually impaired taking the test with either a large print or braille form. Using the Mantel-Haenszel method, only one item at each grade was flagged as displaying large DIF, in each case favoring students without disabilities. Additional items were flagged as exhibiting intermediate DIF, with some items found to favor each group. A priori hypothesis coding and attempts to predict the effects of large print or braille accommodations on DIF were not found to have a relationship with the actual flagging of items, although some a posteriori explanations could be made. The results are seen as supporting the accessibility and validity of the current test for students who are blind or visually impaired while also identifying areas for improvement consisting mainly of attention to formatting and consistency.