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Smoothed Standardization Assessment of Testlet Level DIF on a Math Free-Response Item Type DIF

Dorans, Neil J.; Lyu, C. Felicia; Ramsay, James O.
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Report Number:
ETS Research Report
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Subject/Key Words:
Constructed Responses, Differential Item Functioning (DIF), Kernel Method, Mathematics, Scholastic Assessment Test, Standardization Method, Testlets


A smoothed version of standardization, which merges kernel smoothing with the traditional standardization DIF approach, was used to examine DIF for student produced response (SPR) items on the SAT I Math at both the item and testlet levels. This nonparametric technique avoids model misspecification problems. It also has less sampling errors because of smoothing. Results from the smoothed item-level DIF analysis showed that regular multiple choice items have more variability in DIF values than SPRs. The testlet DIF analysis indicated that White examinees may exceed comparable African American examinees by 14-19 scaled score units on average. Differences between the smoothed standardization and the traditional standardization are small and most likely due to the use of the true score as a matching variable in the smoothed standardization approach. (30pp.)

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