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ERIC Number: EJ1030023
Record Type: Journal
Publication Date: 2014
Pages: 22
Abstractor: As Provided
Reference Count: N/A
ISSN: ISSN-0022-0655
IRT Model Misspecification and Measurement of Growth in Vertical Scaling
Bolt, Daniel M.; Deng, Sien; Lee, Sora
Journal of Educational Measurement, v51 n2 p141-162 Sum 2014
Functional form misfit is frequently a concern in item response theory (IRT), although the practical implications of misfit are often difficult to evaluate. In this article, we illustrate how seemingly negligible amounts of functional form misfit, when systematic, can be associated with significant distortions of the score metric in vertical scaling contexts. Our analysis uses two- and three-parameter versions of Samejima's logistic positive exponent model (LPE) as a data generating model. Consistent with prior work, we find LPEs generally provide a better comparative fit to real item response data than traditional IRT models (2PL, 3PL). Further, our simulation results illustrate how 2PL- or 3PL-based vertical scaling in the presence of LPE-induced misspecification leads to an artificial growth deceleration across grades, consistent with that commonly seen in vertical scaling studies. The results raise further concerns about the use of standard IRT models in measuring growth, even apart from the frequently cited concerns of construct shift/multidimensionality across grades.
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Publication Type: Journal Articles; Reports - Research
Education Level: N/A
Audience: N/A
Language: English
Sponsor: N/A
Authoring Institution: N/A