ABSTRACT
Measurement pervades almost every aspect of modern society. Measurement is generally considered the assigning of numbers to individuals in a systematic way as a means of representing properties of the individuals. For example, a great variety of things about individuals (e.g., achievement, aptitude, intelligence, height, weight) are measured by various people (e.g., teachers, doctors) on a regular basis. At a first glance, to obtain some of these measurements seems quite simple. Unfortunately, a major problem with many kinds of measurements is that there is often no basis to assume that the numerical value provided truthfully and accurately represents the underlying quantity of interest. Because the results of these measurements can have a profound influence on an individual's life, it is important to understand how these scores are derived and the accuracy of the information they contain.
