Standardized Conditional 'SEM': A Case for Conditional Reliability

An examinee-level (or conditional) reliability is proposed for use in both classical test theory (CTT) and item response theory (IRT). The well-known group-level reliability is shown to be the average of conditional reliabilities of examinees in a group or a population. This relationship is similar to the known relationship between the square of the conditional standard error of measurement ("SEM") and the square of the group-level "SEM". The proposed conditional reliability is illustrated with an empirical data set in the CTT and IRT frameworks. (Contains 3 tables.)