Assessing changes in the longitudinal salience of items within constructs

In longitudinal studies, marked changes in item salience may occur even if the internal consistency of a scale remains stable over lime. Such changes in the pattern of response probabilities are relevant for the substantive i nterpretation of the scale scores. Also, there may be interindividual diffe rences in item salience within lime points. The article demonstrates how Ra sch 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 questionnair e does not fulfill the assumptions of the Rasch model, it can be used to ob tain information an item functioning across participants and over lime. The method is illustrated using data from the Baltimore Prevention Program.