Longitudinal studies are permeating clinical trials in psychiatry. Therefore, it is of utmost importance to study the psychometric properties of rating scales, frequently used in these trials, within a longitudinal framework. However, intrasubject serial correlation and memory effects are problematic issues often encountered in longitudinal data.…

Evaluated coefficient alpha under violations of two classical test theory assumptions: essential tau-equivalence and uncorrelated errors through simulation. Discusses the interactive effects of both violations with true and error scores. Provides empirical evidence of the derivation of M. Novick and C. Lewis (1993). (SLD)

This article studies the ordinal reliability of (total) test scores. This study is based on a classical-type linear model of observed score (X), true score (T), and random error (E). Based on the idea of Kendall's tau-a coefficient, a measure of ordinal reliability for small-examinee populations is developed. This measure is extended to large…