The introductory chapter orients students to the basic concepts of scientific research methodology and provides illustrations of the contributions that research can make to police, courts, and corrections. The second chapter explains the basic dichotomies in research methodology, discusses key concepts in research methods, presents examples of the key levels of measurement, and addresses time and its relationship to research studies. Chapter three defines the concept of research design, provides overviews of quantitative and qualitative research designs, and describes evaluation-based research designs. A discussion of data measurement and collection in chapter four focuses on the concept of validity and methods of increasing accuracy in studies, reliability and methods for increasing consistency in studies, quantitative and qualitative data collection, and the three main sources of criminal justice data. Other chapters consider sample selection techniques, experimental designs, survey research, observational designs, secondary analysis of data, basic descriptive analyses, basic inferential analyses, basic qualitative analyses, research ethics, and library research in criminal justice and criminology. Each chapter contains a summary, a statement of main concepts, discussion questions, an exercise, and notes. 168 references, a subject index, and a glossary