In educational and professional contexts, psychological tests are often used to measure, for example, the competence of students or the suitability of applicants. However, for a psychological test to allow for fair comparisons between individuals, it must meet certain requirements. The Rasch model enables the verification of these requirements through its mathematical formulation. It is used, among other things, in empirical educational research for the practical construction of tests and is a standard part of the curriculum in psychology and related fields as the most important representative of so-called probabilistic test theory. This book provides a clear introduction to the topic of constructing and validating psychological tests using the Rasch model. All necessary mathematical and statistical foundations are provided in an appendix and accompanying materials.