An Experimental Template for Case Study Research


  • John Gerring is professor of political science, Boston University, 232 Bay State Road, Boston, MA 02215 ( Rose McDermott is professor of political science, University of California, Santa Barbara, Ellison Hall, University of California, Santa Barbara, Santa Barbara, CA 93106 (

  • For comments and suggestions we are grateful to Jake Bowers, Thad Dunning, and Patrick Johnston, as well as to anonymous reviewers for the journal.


Methods are usually classified as either “experimental” or “observational,” a dichotomy that has governed social science research for centuries. By implication, this dichotomization precludes a consideration of experimental strategies in case study work. Yet, we argue that one gains purchase on the tasks of research design by integrating the criteria traditionally applied to experimental work to all research in the social sciences—including case study work, the focus of this article. Experimental research designs aim to achieve variation through time and across space while maintaining ceteris paribus assumptions, thus maximizing leverage into the fundamental problem of causal inference. We propose to capture these multiple criteria in a four-fold typology: (1) A Dynamic comparison mirrors laboratory experimentation through the use of both temporal and spatial variation; (2) A Longitudinal comparison employs temporal variation; (3) A Spatial comparison exploits variation through space; and (4) A Counterfactual comparison relies on imagined comparison. All comparison case study research designs can be slotted into one of these four categories. Moreover, the typology illustrates in a concise fashion the ways in which case study research designs attempt to mimic the virtues of experimental design and the degree to which they succeed. The classic experiment, with manipulated treatment and randomized control, thus provides a useful template for discussion about methodological issues in experimental and observational contexts.