1: Introduction to Psychometric Concepts

Measurement is a mainstay of educational and psychological practice. Teachers and schools measure student performance through tests, psychologists measure client mood through scales such as the Beck Depression Inventory, and colleges and universities use measurements of scholastic aptitude in making admissions decisions. In all of these cases, the measurement plays a critical role in decision-making about individuals and groups. Therefore, these measurements must be well understood and carefully studied to ensure that they provide the best information possible. Over the last roughly 100 years, a subspecialty combining statistics and educational psychology has developed in order to study such measures. This field, known as psychometrics, focuses on the development and vetting of educational and psychological assessments using a wide variety of tools. Together, these tools represent a wide array of statistical analyses that can provide the researcher with a great deal of information regarding the performance of a particular measure. We will cover many of these tools together in this book, focusing on how SAS software can be used to obtain information about individual items as well as the scale as a whole.