Fig. 3
From: Assessing adolescents’ perceived proficiency in critically evaluating nutrition information
Step 1 tests the null hypothesis that the restricted rating scale parameterization (RSM) describes the data as well as the more complex partial credit parameterization (PCM) of the polytomous unidimensional Rasch model (PCM). Step 2 investigates dimensionality, comparing fit to the PCM of the 1-dimensional scale and a 2-dimensional scale. In the 2-dimensional scale, the items are categorized into two ‘sub-dimensions’ i.e., items 1, 2, 3 and items 4 and 5, based on qualitative interpretation of item content, confirmed by the PCA/t-test procedure in RUMM2030. The dashed arrow indicates that the 1-dim PCM is the preferred parameterization