This book is intended for university students who are studying a degree in psychology, and also for professional psychologists who wish to improve the techniques of validation of a test. It contains techniques of the Classical Theory Test, Item Response Theory, with examples of the application of each technique. The CTT includes validation techniques using Principal Components Analysis, Unidimensionality of Scales (among others), calculation of Coefficients of Reliability, calculation of indices related to the items (difficulty, discrimination), etc. And with respect to the IRT, you will find models for dichotomous items (such as the Rasch model), and models for polytomous items.