Ligtvoet, Rudy

Models and methods for invariant item ordering

Affiliation:   Department of Methodology, Faculty of Social Sciences, Tilburg University

Project running from: 1 January 2006 – 1 January 2010

Project financed by:  Tilburg University

Promotores: Prof. dr K. Sijtsma, prof. dr J.K. Vermunt, dr A. Van der Ark

Items in a test or a questionnaire have an invariant item ordening (IIO) if the items have an identical ordering according to difficulty or atractiveness for every individual in the population of interest, with the exeption of possible ties. Several applications of test results require an IIO. Examples are the investigation of developmental theories, differential item functioning, aberrant response patterns, and the use of starting and stopping rules in administration. This PhD project proposal contains four parts, each investigating different aspects of the ordering of polytomous items in a test or questionnaire. The first project aims at the development of an item response theory model, which implies an invariant item ordering of polytomous items, which implies an invariant ordering. The psychometric properties of these models will be investigated. Second, methods for testing the invariant ordering of polytomous items, which have not yet been investigated thoroughly, are further developed and compared. Third, the use of latent class analysis as a tool for estimating item orderings is explored. Fourth, the newly developed models and methods are applied in the real data.

Date of defence: 16 April 2010

Title of thesis: Essays on invariant item ordering