Studying group and time invariance in maximal reliability for multiple-component measuring instruments via covariance structure modelling.

A method for examining invariance in maximal reliability for weighted combinations of congeneric measures is described. The approach is developed within the framework of covariance structure modelling and allows one to ascertain whether a multi-component instrument consisting of homogeneous measures is associated with the same minimal relative error variance in distinct populations or over time. The procedure yields as a by-product an interval measure of discrepancy in maximal reliability across independent groups or assessment occasions, and is illustrated with two examples.