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Moses, Tim; Liu, Jinghua – Educational Testing Service, 2011
In equating research and practice, equating functions that are smooth are typically assumed to be more accurate than equating functions with irregularities. This assumption presumes that population test score distributions are relatively smooth. In this study, two examples were used to reconsider common beliefs about smoothing and equating. The…
Descriptors: Equated Scores, Data Analysis, Scores, Methods
Moses, Tim; Miao, Jing; Dorans, Neil – Educational Testing Service, 2010
This study compared the accuracies of four differential item functioning (DIF) estimation methods, where each method makes use of only one of the following: raw data, logistic regression, loglinear models, or kernel smoothing. The major focus was on the estimation strategies' potential for estimating score-level, conditional DIF. A secondary focus…
Descriptors: Test Bias, Statistical Analysis, Computation, Scores
von Davier, Matthias; Xu, Xueli; Carstensen, Claus H. – Educational Testing Service, 2009
A general diagnostic model was used to specify and compare two multidimensional item-response-theory (MIRT) models for longitudinal data: (a) a model that handles repeated measurements as multiple, correlated variables over time (Andersen, 1985) and (b) a model that assumes one common variable over time and additional orthogonal variables that…
Descriptors: Models, Item Response Theory, Longitudinal Studies, Measurement