In the absence of clear incentives, achievement tests may be subject to the effect of slipping where item response functions have upper asymptotes below one. Slipping reduces score precision for higher latent scores and distorts test developers' understandings of item and test information. A multidimensional four-parameter normal ogive model was…

In this article, we consider estimation of parameters of random effects models from samples collected via complex multistage designs. Incorporation of sampling weights is one way to reduce estimation bias due to unequal probabilities of selection. Several weighting methods have been proposed in the literature for estimating the parameters of…

Problems of scale typically arise when comparing test score trends, gaps, and gap trends across different tests. To overcome some of these difficulties, test score distributions on the same score scale can be represented by nonparametric graphs or statistics that are invariant under monotone scale transformations. This article motivates and then…