Dutch Railways CAT

Wouter Schoonman's "An applied study on computerized adaptive testing" (Rockland MA: Swets & Zeitlinger, 1989) is a treasury of useful CAT information for the discerning, but occasionally skeptical, reader. Schoonman's aim was to construct a CAT system for the Dutch version of the General Aptitude Test Battery (GATB). For this endeavor, he perused the literature (providing a comprehensive reference list) and consulted the best minds in The Netherlands.

Naturally, he encountered the usual CAT dragons. He found that many specialists favor fitting elaborate psychometric models to their responses. Nevertheless, the exigencies of missing data, small sample sizes and the need to construct a useful item bank forced him to his own conclusion: "advantages outweigh the disadvantages in favor of the use of the [Rasch] model."

His choice of an item selection algorithm was dominated by the customary superstitions: 1) accurate measurement requires precise item pre-calibration, 2) all the benefits of CAT ride on managing to administer the absolute minimum number of items, and 3) the CAT algorithm must be complicated to be good. Fortunately, the description Schoonman gives of his complicated Bayesian algorithm is sufficiently opaque to inhibit others from trying to copy this part of his work. The main benefit he claims for his Bayesian algorithm is that it produces uniform measurement error. But a stop rule based on the standard error of measurement, which does just that, can be implemented with the simplest "PROX"-like CAT algorithm (Linacre 1988).

Schoonman uses three personality inventories to investigate examinees' attitudes to computers and test-taking behavior. He did not detect any strong interactions between personality traits and test results.

Schoonman also discusses the practical problems of converting GATB items from their speeded written form to the power-oriented computer- administered form. He discovered that, when the written version is administered to an examinee first and immediately followed by the CAT version, then speeded test-taking strategies are used by the examinee for the CAT power test. The result is a CAT score lower than expected. This provokes Schoonman into investigating response time, and he discovers that, for the GATB, it is inversely correlated with ability. He went no further for lack of a psychometric model for speeded tests. His next step could be to read Rasch (1960) Chapters 2-4.

Linacre JM 1988. Computer-adaptive testing: Simple and effective algorithms. AERA Annual Meeting. New Orleans. ERIC ED 294 918

Rasch G 1960, 1980. Probabilistic models for some intelligence and attainment tests. Chicago: Chicago University Press.

Dutch Railways CAT, W Schoonman … Rasch Measurement Transactions, 1991, 5:2 p. 144

Rasch Publications
Rasch Measurement Transactions (free, online)	Rasch Measurement research papers (free, online)	Probabilistic Models for Some Intelligence and Attainment Tests, Georg Rasch	Applying the Rasch Model 3rd. Ed., Bond & Fox	Best Test Design, Wright & Stone
Rating Scale Analysis, Wright & Masters	Introduction to Rasch Measurement, E. Smith & R. Smith	Introduction to Many-Facet Rasch Measurement, Thomas Eckes	Invariant Measurement: Using Rasch Models in the Social, Behavioral, and Health Sciences, George Engelhard, Jr.	Statistical Analyses for Language Testers, Rita Green
Rasch Models: Foundations, Recent Developments, and Applications, Fischer & Molenaar	Journal of Applied Measurement	Rasch models for measurement, David Andrich	Constructing Measures, Mark Wilson	Rasch Analysis in the Human Sciences, Boone, Stave, Yale
in Spanish:	Análisis de Rasch para todos, Agustín Tristán		Mediciones, Posicionamientos y Diagnósticos Competitivos, Juan Ramón Oreja Rodríguez

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