Resolving the test–retest agreement or reliability dilemma

Abstract

Agreement refers to the degree to which an individual i ’s test scores match in test–retest settings. Agreement has been thought to be unapproachable with correlational reliability indices. Stable unstable reliability theory extends Spearman’s reliability model and specifies the probability that i ’s test–retest true scores match. Thus, agreement and reliability are simultaneously addressed. Two examples, one using longitudinal data, illustrate the procedure.