Reliability if deleted, not 'alpha if deleted': evaluation of scale reliability following component deletion.

This paper demonstrates that the widely available and routinely used index 'coefficient alpha if item deleted' can be misleading in the process of construction and revision of multiple-component instruments with congeneric measures. An alternative approach to evaluation of scale reliability following deletion of each component in a given composite is outlined that can be recommended in general for scale development purposes. The method provides ranges of plausible values for instrument reliability when dispensing with single components in a tentative composite, and permits testing hypotheses about reliability of resulting scale versions. The proposed procedure is illustrated with an example.