Comment: Are Marginal Models Needed?
Nanny Wermuth · Sociological Methodology · 2013
It is a pleasure to comment on three papers, where each provides substantial new work and each mentions marginal models in the title. The paper by Kuijpers, Van der Ark, and Croon (this volume, p. 42–69) presents developments in the construction of scales for cate-gorical variables. A sequence of papers has been published in recent years in the psychometric literature on properties of this type of non-parametric scale construction for binary and polytomous items. The items here are the observed variables, each having the same number of categories or levels. A first program version for analyses was integrated several years ago into the computing environment R and updated recently by Van der Ark (2012). As a result, a well-written, thoughtful use of this type of analysis is, for instance, now available for health researchers, as discussed in Stochl, Jones, and Croudace (2012). The earliest discussions of these scales appear to be by Loevinger