ASSESSING THE EFFECT OF COHORT, GENDER, AND RACE ON DIFFERENTIAL ITEM FUNCTIONING (DIF) IN AN ADAPTIVE TEST DESIGNED FOR MULTI-AGE GROUPS

Differential item functioning (DIF) statistics were computed using items from the Peabody Individual Achievement Test (PLAT)-Reading Comprehension subtest for children of the same age group (ages 7 through 12 respectively). The pattern of observed DIE items was determined by comparing each cohort across age groups. Differences related to race and gender were also identified within each cohort. Characteristics of DIF items were identified based on sentence length, vocabulary frequency, and density of a sentence. DIE items were more frequently associated with short sentences than with long sentences. This study explored the potential limitation in the longitudinal use of items in an adaptive test.