In Ramsay curve item response theory (RC-IRT, Woods & Thissen, 2006) modeling, the shape of the latent trait distribution is estimated simultaneously with the item parameters. In its original implementation, RC-IRT is estimated via Bock and Aitkin's (1981) EM algorithm, which yields maximum marginal likelihood estimates. This method, however,…

The problem of the additive constant is the problem of making interval data approximate ratio data. This paper discusses some issues concerning the additive constant and presents a new formulation of and solution for the problem. (JKS)

Alternating least squares and optimal scaling are presented as two approaches to the quantitative analysis of qualitative data. A variety of statistical approaches to this problem are discussed. Three examples are presented. (JKS)

The degree to which Procrustean Individual Differences Scaling can be extended to related topics such as target analysis is discussed and a Monte Carlo study investigating the fit of the model under various conditions is presented. (JKS)

Six major problems confronting attempts to use nonmetric multidimensional scaling to represent structures underlying similarity data are identified and the author's prospects for over-coming each of these problems are presented. (RC)

A method of nonmetric multidimensional scaling is described which minimizes pairwise departures from monotonicity. (Author)

The usefulness of the general Rasch model for multidimensional data, from the most simple formulations to the more complex versions of the model, is explored. Also investigated was whether the parameters of the models could be readily interpreted. Models investigated included: (1) the vector model; (2) the product term model; (3) the vector and…

Concerned with another form of analysis of m sets of matrices, the Procrustes idea is generalized so that all m sets are simultaneously translated, rotated, reflected and scaled so that a goodness of fit criterion is optimised. A computational technique is given, results of which can be summarized in analysis of variance form. (RC)

This study assessed the construct validity of a cognitive structure interpretation of multidimensional scaling solutions of concept similarity data. Using high school subjects, convergent validity was assessed through correspondence of scaling solutions of three similarity rating tasks; word association, similarity judgment, and semantic…