Assessing Changes in the Longitudinal Salience of Items within Constructs

Abstract

In longitudinal studies, marked changes in item salience may occur even if the internal consistency of a scale remains stable over time.Such changes in the pattern of response probabilities are relevant for the substantive interpretation of the scale scores.Also, there may be interindividual differences in item salience within time points.The article demonstrates how Rasch models can be used to study item salience within and across time points.Also, the authors want to demonstrate that even if a test or questionnaire does not fulfill the assumptions of the Rasch model, it can be used to obtain information on item functioning across participants and over time.The method is illustrated using data from the Baltimore Prevention Program.