The vertical scales of large-scale achievement tests created by using item response theory (IRT) models are mostly based on cluster (or correlated) educational data in which students usually are clustered in certain groups or settings (classrooms or schools). While such application directly violated assumption of independent sample of person in…

The purpose of this paper is to prove that one currently recommended method of obtaining the reliability of an instrument defined on a population of aggregate units is invalid. This method randomly splits the aggregate into two halves, correlates the two half unit scores by a Pearson product moment correlation coefficient, and corrects the…

To examine the validity of short forms of the Wechsler Intelligence Scale for Children-Revised (WISC-R), the WISC-R was first administered to 106 hospitalized psychiatric patients, aged 8-16. No subjects had a primary diagnosis of mental retardation or learning disability, and one-third were receiving psychotropic medication. WISC-R IQ scores…