This course offers a comprehensive exploration of the theoretical and practical aspects of psychometric testing, with a particular focus on classical test theory (CTT) and its application in psychological assessment. Students are introduced to the foundational principles of measurement, which underpin the development and evaluation of psychological tests. The curriculum begins with an overview of psychometric testing and classical test theory, highlighting its axioms, models, and relevance for modern psychological measurement. A key component of the course is the study of latent and manifest variables. Latent variables represent underlying psychological traits or constructs that cannot be observed directly, while manifest variables are the observable outcomes measured through tests. Understanding the distinction and interplay between these variables is essential for designing effective assessment tools and interpreting test results accurately. The principles of measurement are discussed in detail, emphasising their importance in ensuring the validity and reliability of psychological assessments. Students learn to apply statistical methods to verify psychometric properties, including reliability estimation and model verification. Techniques such as reliability analysis enable students to assess the consistency and trustworthiness of measurement instruments, which are crucial for both research and practical applications in psychology. The course guides students through the process of test and item construction, providing guidelines and best practices for developing meaningful and effective test items. Both qualitative and quantitative methods are covered, including item development and validation techniques. Exploratory factor analysis is introduced as a tool for examining the structure of psychological constructs and refining measurement instruments. Students gain hands-on experience with statistical software, such as R, for data handling, reliability analysis, and exploratory factor analysis. The application of R enhances students’ ability to perform sophisticated statistical analyses and validate psychological tests with scientific precision. Throughout the module, emphasis is placed on scientific rigour and ethical standards in psychometric diagnostics. By the end of the course, students are equipped to design, construct, and validate psychological measurement tools, demonstrating an understanding of both theoretical foundations and practical applications. The course objectives and outcomes reinforce the development of essential skills in psychometric testing, preparing students and educators to engage confidently with psychological assessment and research.