The design and implementation of reliable and valid studies in health sciences are prerequisites for drawing safe conclusions, improving clinical practice, and applying rational healthcare. This book aims precisely in this direction. It analyzes the sequential steps of designing and conducting a study, from the conception of the research hypothesis to completion. Furthermore, each step is presented in a simple, clear, and detailed manner with the use of appropriate examples. The second revised edition of the book covers both qualitative and quantitative research, enabling readers to understand with simple examples how these two types of research are applied in everyday clinical practice. The simplicity and clarity of this edition aim to enable even researchers at their early stages, such as health science students, to initially understand the design of studies and subsequently proceed with their implementation.