Mokken scale analysis for polychotomous items: theory, a computer program and an empirical application

R. J. Mokken's approach (A Theory and Procedure of Scale Analysis, The Hague: Mouton, 1971) for dichotomously scored items is reviewed, & extended to multicategory items with ordered response categories. Relevant technical information on MSP, a computer program for analyzing multicategory item scores, is provided & applied to data from an investigation of the attitudes of delegates (N = 806) of Dutch political parties collected by B. P. Middel & W. H. van Schuur ("Dutch Party Delegates," Acta Politica, 1981, 16, 241-243). Results are compared to those from the original investigation & suggest that the extension of the Mokken model to multicategory item scores enables the researcher to avoid losing information resulting from a dichotomization of originally multicategory data. Results show that the composition of scales based on polychotomous & dichotomized data may be different. 5 Tables, 20 References. L. Taub