What conclusions can be drawn when a reduction in symptoms is observed in 20 depressed individuals after psychotherapy? That psychotherapy is effective? Or was it just coincidence? A key objective of empirical research is to make generalizable statements about facts. To avoid hasty and incorrect conclusions, inferential statistics is employed. This book provides a clear introduction to its logic with a variety of examples and presents central methods of hypothesis testing. The reader thus gains an understanding of fundamental principles of inferential statistics, which will later allow for a better comprehension of more complex applications.