https://lloyd-hoff.thoughtlanes.net/basics-of-psychometric-foundations-1734607015 Psychometric techniques are vital for measuring the psychological attributes of individuals. These methods are implemented in numerous fields, including educational assessment, employment testing, clinical diagnosis, and research. This article provides a comprehensive analysis of key psychometric techniques, highlighting their methodologies, applications, and the intricacies involved in their implementation. Overview of Classical Test Theory Synopsis: Classical Test Theory (CTT) is one of the most established psychometric frameworks. It posits that an observed score is the sum of a true score and an error score. This theory emphasizes the reliability and validity of test scores. Fundamental Concepts: Reliability, which measures the consistency of test scores over time, is gauged using coefficients such as Cronbach’s alpha, split-half reliability, and test-retest reliability. Validity: The extent to which a test measures what it purports to measure. Types of validity include content, construct, and criterion-related validity. Practical Applications: CTT is commonly used in educational and psychological testing due to its simplicity and ease of interpretation. It helps in test development, ensuring that assessments are both reliable and valid. Constraints: CTT posits that all items on a test contribute equally to the total score and that measurement error is the same across all levels of the trait being measured, which can be unrealistic. Introduction to Item Response Theory Synopsis: Item Response Theory (IRT) provides a probabilistic framework to understanding the relationship between an individual's latent trait (e.g., ability or attitude) and their item responses. Unlike CTT, IRT accounts for the difficulty and discrimination of each item. Main Models: The One-Parameter Logistic Model (1PL) considers only item difficulty. Two-Parameter Logistic Model (2PL): Considers both item diffic