Psychometric theory is a branch of psychology that deals with the measurement of psychological attributes, such as intelligence, personality traits, and attitudes. It provides a scientific approach to understanding individual differences and developing assessments to measure these differences. One of the most influential figures in psychometric theory is Jum Nunnally, whose work has had a lasting impact on the field. In this article, we will explore Nunnally's contributions to psychometric theory and provide an overview of the key concepts and PDF resources available.

Unlike CTT, which evaluates the test as a whole, IRT evaluates the performance of individual test items based on difficulty and discrimination parameters. Nunnally’s inclusion of these concepts bridged the gap between traditional 20th-century testing and modern adaptive testing algorithms used today. 7. Ethical and Legal Access to Psychometric Literature

How well the test scores correlate with an external, concrete outcome (e.g., SAT scores predicting college GPA).

Reliability alone is not enough; a scale can be perfectly consistent but measure the entirely wrong thing. Nunnally dedicated significant portions of Psychometric Theory to validity, categorizing it into three primary frameworks: Content Validity