Through the use of specific examples to illustrate evaluation research goals and methods, Thinking About Program Evaluation provides readers with an overview of the science and politics of evaluation research. New to this edition is coverage of meta-analysis, selection models, and instrumental variables. In addition, the authors have expanded the coverage of analysis of data, evaluation when the units of analysis are entire organizations of political jurisdictions, and comparisons between evaluation research and other related fields. The rich mix of examples has been expanded to include more illustrations from environmental evaluation, and the most recent studies on welfare reform, managed mental health care, and law enforcement.