1: As a field, we have traditionally referred to scales as “reliable” or “unidimensional”, but methodologists since Lord & Novick (1968) caution that instruments do not have reliability, only scores from particular samples do. (See also Wilkinson and the Task Force on Statistical Inference, 1999.) Despite this, we should have a reasonable expectation for instruments to have the same basic structure across samples if we are to have any rational basis for the science of measurement within the social sciences. [return]

2: We could go on for many more pages summarizing various historical approaches to summarizing congruence. For the sake of parsimony we will simply refer the readers to the above-cited resources that give thorough coverage of the issues. [return]