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Using DIF Dissection Method to Assess Effects of Item Deletion SAT DIF

Author(s):
Zhang, Yanling; Dorans, Neil J.; Matthews-Lopez, Joy L.
Publication Year:
2005
Report Number:
RR-05-23, CBR-2005-10
Source:
ETS Research Report
Document Type:
Report
Page Count:
11
Subject/Key Words:
SAT, Differential Item Functioning (DIF), Standardization Method, DIF Dissection Approach, Two-Way DIF Classification

Abstract

Statistical procedures for detecting differential item functioning (DIF) are often used as an initial step to screen items for construct irrelevant variance. This research applies a DIF dissection method and a two-way classification scheme to SAT Reasoning Test™ verbal section data and explores the effects of deleting sizable DIF items on reported scores after re-equating. The DIF dissection approach and the two-way classification scheme may yield new and detailed insight into item functioning at the subgroup level. Two hypotheses are studied: (a) whether or not the deletion of a sizeable DIF item that is the most disadvantageous to a particular subgroup will affect the scores for that subgroup the most and (b) whether or not the effects of item deletion on scores can be predicted by the standardization method. Both hypotheses are supported by the results of this research.

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