A-priori Weighting of Items with the Rasch Model

Many assessment scales in the social sciences are composed of multiple items that form a subscale structure. They have this structure because more than one aspect of the variable is assessed and more than one item assesses each aspect. Nevertheless, generally, a single measurement is required from the scale. A characteristic of this measurement is that the greater the number of items, and categories within an item, that assess an aspect, the greater its influence on the final measurement. One way to control this influence is to include the desired relative number of items and categories to assess each aspect in the scale. However, there are circumstances where designing the required number of items and categories for each aspect is challenging. This paper shows a method of controlling the influence of the number of items and categories assessing each aspect by a-priori weighting of items at the person measurement stage with the Rasch model.