Substantive scale construction

Variable construction requires careful attention to substantive issues; a theory guiding its development, a hierarchy of illustrative items constructed to define the variable, the subsequent production of item difficulties and person measures, and the analysis of fit. Rasch measurement practitioners should give careful attention to these matters so practical suggestions are given for designing variables based on theory, item construction, and Rasch models for the analysis of data. Variable maps are emphasized to guide variable construction and interpret the results.