The chapter on the purpose of criminal justice research advises that such research is about the generation of information that is both accurate and objective for the purpose of guiding criminal justice decisionmaking. The chapter on library research and literature reviews pertains to the identification of information that is already known on a particular topic. The chapter on ethical issues in criminal justice research discusses ethical considerations in criminal justice research before, during, and after a research project. The chapter on measuring crime addresses the validity and reliability of crime data sources, with attention to the major national systems that collect and report crime data. Issues in self-report crime data are also discussed. The chapter on elements of research design reviews the types of research design and threats to internal and external validity. This is followed by a chapter on the principles of sampling, which discusses types of samples and presents examples of sampling in criminal justice research. Concepts in scaling, types of scales, potential uses of measurement scales, and the creation of a measurement scale are considered in the next chapter. A chapter then focuses on observational studies in qualitative research, with attention to participant observation, the selection of a setting, and recording and analyzing the data. The book concludes with chapters on qualitative interviews and designing and conducting criminal justice evaluation research. Each chapter contains an overview of its contents, a conclusion, key terms, review questions, and references.