Comparative Case Study

Conceptual Overview and Discussion

The comparative case study can achieve any of the principal goals of the general case study approach and is not limited in terms of descriptive, exploratory, or explanatory goals. Within this broad context, the comparative aspect of the case study can have either a qualitative or quantitative focus. Comparative case studies tend toward an examination of the typical rather than the outlier or extreme case. Generally, research into the unusual, rare, or revelatory has not been appropriate for multiple-case designs, simply because selected cases must demonstrate enough commonality to allow for comparison.

Robert Yin, who has written extensively on case study research, states that comparative case studies are multiple experiments and not instances of multiple subjects across a single experiment. In case comparison, several cases serve as replication sites for extension or surfacing of theory. Cases may also be viewed as a replication of the instance or phenomenon, similar to an experiment in a quantitative undertaking. These comparisons can be structured as either between-case or within-case studies. Within-case studies, for example, might include several organizations within a specific [Page 175]industry, cohorts from a particular educational institution, or negotiations between a single country and several allies.

The comparative case approach uses an iterative analysis of each case with final comparison of emergent themes and explanations. The results of each analysis are not pooled, as the strategy is that of multiple experiments, not multiple sampling. Comparison of cases is post hoc in nature, and may be independent of the level of analysis of the case. A longitudinal design is also possible, with one or more instances or sites serving as separate case studies over time. One variation of this is a pilot study, which Robert Yin has used to define an analytical framework and to refine instruments and research tactics.

The case survey is a variant of the comparative case study that views cases chosen for research as a series of data points from which comparison and analysis will be possible. The case survey produces a sample size of hundreds of cases, from which researchers draw out of the detail of their analysis the critical components or factors that are interesting enough to warrant the study. To find comparable sites for this type of research is challenging in any context, and the depth of detail generated through the case survey produces two complicating effects in this form of the case study: increased effort (translating into costs) and the risk of noncomparability due to variations in significant contextual factors. The case survey represents the worst of a quantitative–qualitative mixed approach, particularly when the factor of interest is unduly simplified in order to make volumes of data more manageable.

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