TY - JOUR
T1 - An NCME instructional module on using differential step functioning to refine the analysis of dif in polytomous items
AU - Penfield, Randall D.
AU - Gattamorta, Karina
AU - Childs, Ruth A.
PY - 2009/3/1
Y1 - 2009/3/1
N2 - Traditional methods for examining differential item functioning (DIF) in polytomously scored test items yield a single item-level index of DIF and thus provide no information concerning which score levels are implicated in the DIF effect. To address this limitation of DIF methodology, the framework of differential step functioning (DSF) has recently been proposed, whereby measurement invariance is examined within each step underlying the polytomous response variable. The examination of DSF can provide valuable information concerning the nature of the DIF effect (i.e., is the DIF an item-level effect or an effect isolated to specific score levels), the location of the DIF effect (i.e., precisely which score levels are manifesting the DIF effect), and the potential causes of a DIF effect (i.e., what properties of the item stem or task are potentially biasing). This article presents a didactic overview of the DSF framework and provides specific guidance and recommendations on how DSF can be used to enhance the examination of DIF in polytomous items. An example with real testing data is presented to illustrate the comprehensive information provided by a DSF analysis.
AB - Traditional methods for examining differential item functioning (DIF) in polytomously scored test items yield a single item-level index of DIF and thus provide no information concerning which score levels are implicated in the DIF effect. To address this limitation of DIF methodology, the framework of differential step functioning (DSF) has recently been proposed, whereby measurement invariance is examined within each step underlying the polytomous response variable. The examination of DSF can provide valuable information concerning the nature of the DIF effect (i.e., is the DIF an item-level effect or an effect isolated to specific score levels), the location of the DIF effect (i.e., precisely which score levels are manifesting the DIF effect), and the potential causes of a DIF effect (i.e., what properties of the item stem or task are potentially biasing). This article presents a didactic overview of the DSF framework and provides specific guidance and recommendations on how DSF can be used to enhance the examination of DIF in polytomous items. An example with real testing data is presented to illustrate the comprehensive information provided by a DSF analysis.
KW - Differential item functioning
KW - Graded response model
KW - Polytomous items
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U2 - 10.1111/j.1745-3992.2009.01135.x
DO - 10.1111/j.1745-3992.2009.01135.x
M3 - Article
AN - SCOPUS:60249091295
VL - 28
SP - 38
EP - 49
JO - Educational Measurement: Issues and Practice
JF - Educational Measurement: Issues and Practice
SN - 0731-1745
IS - 1
ER -