Examining temporal stability of scale validity in longitudinal studies

A method for examining invariance in validity of multiple-component instruments in repeated measure designs is outlined. The approach is developed within the framework of covariance structure modeling and is applicable for purposes of ascertaining temporal stability in scale validity. In addition, the procedure provides a range of plausible values in a population under investigation for the change in composite validity across longitudinal assessment occasions. The proposed method can also be used to examine possible sources of lack of validity invariance, and is illustrated with a pair of examples.