Now in its fifth edition, this classic text helps readers learn how to design, conduct, analyze, and report high-quality clinical studies. Alan E. Kazdin brings together a wide array of authoritative articles with his own expert insights to illustrate fundamental issues research in an accessible manner, including generating ideas, selecting participants, randomization, selecting assessment measures, analyzing data, and evaluating the implications of and publishing the results.   New to this edition are articles emphasizing the importance of diversity in research, not only cultural diversity among study participants but also in methodology (including quantitative, qualitative, and mixed methods); the role of big data; using technology such as artificial intelligence and apps; and strategies to improve transparency and accessibility, including open science practices, replication, and preregistration. From generating hypotheses for study and selecting appropriate assessments to interpreting data and presenting findings, readers will come to better understand the whole research process as well as the importance of ethics and scientific integrity.