Qualitative Comparative Analysis (QCA) is a set-theoretic method for descriptive and causal inference. This page gathers everything QCA-related: my Georgetown UP book, summer school teaching & workshops, the R Manual for QCA, replication data, and applied studies.
The Book
Mello, Patrick A. 2021. Qualitative Comparative Analysis: An Introduction to Research Design and Application. Washington, DC: Georgetown University Press.
Harvard DataverseQCAResearch designSet theoryCase study researchRQualitative Comparative Analysis: An Introduction to Research Design and Application (Georgetown University Press, 2021 with a second edition under contract) is a comprehensive guide to QCA — from research design to calibration, analysis, and interpretation. More on the book page.
See also the Routledge Handbook of Foreign Policy Analysis Methods (2023), which includes a chapter on QCA.
R Manual for QCA (Version 4, 2026)
The book is complemented by an online R Manual for QCA. This is regularly updated (current version: 4, July 2026). All instructions are contained in the PDF file, all code is included in the R Script, which works with the two sample data sets. The files are also available through Harvard Dataverse. If you run into errors or if questions arise, please let me know.
Summer School Course & Workshops
- QCA — Summer School in Social Sciences Methods, Lugano (FORS), annual one-week course.
- I regularly teach QCA workshops at universities and public institutions — see Teaching for the full list.
Talks
ISA Talk on Qualitative Comparative Analysis (YouTube).
Video summary of Qualitative Comparative Analysis: An Introduction to Research Design and Application (YouTube).
Applied Work
A selection of my articles and chapters that apply QCA or discuss its use (full details under Publications). Replication data and additional documentation for my research is hosted at Harvard Dataverse.
Books
Mello, Patrick A. 2014. Democratic Participation in Armed Conflict: Military Involvement in Kosovo, Afghanistan, and Iraq. Basingstoke: Palgrave Macmillan.
Articles
Caputo, Alessia, Lorenzo Taddeucci, Patrick A. Mello, and Milena Vainieri. 2026. Can the Public Sector Break the Mold? Exploring Antecedent Factors Driving Sensing Capabilities With fsQCA in the Tuscan Family and Community Nurse Model. Public Policy and Administration (June 8, 2026), 1-38.
Mello, Patrick A. 2022. Incentives and Constraints: A Configurational Account of European Involvement in the Anti-Daesh Coalition. European Political Science Review 14 (2), 226-244.
Ide, Tobias, and Patrick A. Mello. 2022. QCA in International Relations: A Review of Strengths, Pitfalls, and Empirical Applications. International Studies Review 24 (1), 1-20.
C. Heldt, Eugénia, Patrick A. Mello, Anna Novoselova, and Omar Ramon Serrano Oswald. 2022. When Do International Organizations Engage in Agency Slack? A Qualitative Comparative Analysis of United Nations Institutions. Global Studies Quarterly 2 (3), 1-15.
Meissner, Katharina L., and Patrick A. Mello. 2022. The Unintended Consequences of UN Sanctions: A Qualitative Comparative Analysis. Contemporary Security Policy 43 (2), 243-273.
Mello, Patrick A. 2020. Paths towards Coalition Defection: Democracies and Withdrawal from the Iraq War. European Journal of International Security 5 (1), 45-76.
Mello, Patrick A. 2012. Parliamentary Peace or Partisan Politics? Democracies’ Participation in the Iraq War. Journal of International Relations and Development 15 (3), 420-453.
Chapters
Mello, Patrick A. 2024. Uncovering Causal Complexity with Qualitative Comparative Analysis. In The Handbook of Teaching Qualitative and Mixed Research Methods: A Step-by-Step Guide for Instructors, edited by Alissa Ruth, Amber Wutich, and H. Russell Bernard. London: Routledge, 336-339.
Mello, Patrick A. 2023. Qualitative Comparative Analysis. In Routledge Handbook of Foreign Policy Analysis Methods, edited by Patrick A. Mello and Falk Ostermann. London: Routledge, 385-402.
Mello, Patrick A. 2017. Qualitative Comparative Analysis and the Study of Non-State Actors. In Researching Non-State Actors in International Security: Theory & Practice, edited by Andreas Kruck and Andrea Schneiker. London: Routledge, 123-142.