Case studies involve a particular method of research. Rather than using large samples and following a rigid protocol to examine a limited number of variables, case study methods involve an in-depth, longitudinal examination of a single instance or event. They provide a systematic way of looking at events, collecting data, analyzing information, and reporting the results. As a result the researcher may gain a sharpened understanding of why the instance happened as it did, and what might become important to look at more extensively in future research. Case studies lend themselves especially to generating (rather than testing) hypotheses.
Certain disciplines thrive on case studies: others find them less suitable in given situations. Compare usage and perceived validity in the humanities, natural sciences, social sciences, pseudoscience and business.
Illustrative case studies describe a domain; they utilize one or two instances to analyze a situation. This helps interpret other data, especially when researchers have reason to believe that readers know too little about a program. These case studies serve to make the unfamiliar familiar, and give readers a common language about the topic. The chosen site should typify important variations and contain a small number of cases to sustain readers' interest.
The presentation of illustrative case studies may involve some pitfalls. Such studies require presentation of in-depth information on each illustration; but the researcher may lack time on-site for in-depth examination. The most serious problem involves the selection of instances. The case(s) must adequately represent the situation or program. Where significant diversity exists, no single individual site may cover the field adequately.
Exploratory case studies condense the case study process: researchers may undertake them before implementing a large-scale investigation. Where considerable uncertainty exists about program operations, goals, and results, exploratory case studies help identify questions, select measurement constructs, and develop measures; they also serve to safeguard investment in larger studies.
The greatest pitfall in the exploratory study involves premature conclusions: the findings may seem convincing enough for inappropriate release as conclusions. Other pitfalls include the tendency to extend the exploratory phase, and inadequate representation of diversity.
Critical instance case studies examine one or a few sites for one of two purposes. A very frequent application involves the examination of a situation of unique interest, with little or no interest in generalizability. A second, rarer, application entails calling into question a highly generalized or universal assertion and testing it by examining one instance. This method particularly suits answering cause-and-effect questions about the instance of concern.
Inadequate specification of the evaluation question forms the most serious pitfall in this type of study. Appropriate application of the critical instance case study crucially involves probing the underlying concerns in a request.
Program implementation case studies help discern whether implementation complies with intent. These case studies may also prove useful when concern exists about implementation problems. Extensive, longitudinal reports of what has happened over time can set a context for interpreting a finding of implementation variability. In either case, researchers aim for generalization and must carefully negotiate the evaluation questions with their customer.
Good program implementation case studies must invest sufficient time to obtain longitudinal data and breadth of information. They typically require multiple sites to answer program implementation questions; this imposes demands on training and supervision needed for quality control. The demands of data management, quality control, validation procedures, and analytic modelling (within site, cross-site, etc.) may lead to cutting too many corners to maintain quality.
Program effects case studies can determine the impact of programs and provide inferences about reasons for success or failure. As with program implementation case studies, the evaluation questions usually require generalizability and, for a highly diverse program, it may become difficult to answer the questions adequately and retain a manageable number of sites. But methodological solutions to this problem exist. One approach involves first conducting the case studies in sites chosen for their representativeness, then verifying these findings through examination of administrative data, prior reports, or a survey. Another solution involves using other methods first. After identifying findings of specific interest, researchers may then implement case studies in selected sites to maximize the usefulness of the information.
Cumulative case studies aggregate information from several sites collected at different times. The cumulative case study can have a retrospective focus, collecting information across studies done in the past, or a prospective outlook, structuring a series of investigations for different times in the future. Retrospective cumulation allows generalization without cost and time of conducting numerous new case studies; prospective cumulation also allows generalization without unmanageably large numbers of cases in process at any one time.
The techniques for ensuring sufficient comparability and quality and for aggregating the information constitute the "cumulative" part of the methodology. Features of the cumulative case study include the case survey method (used as a means of aggregating findings) and backfill techniques. The latter aid in retrospective cumulation as a means of obtaining information from authors that permits use of otherwise insufficiently detailed case studies.
Opinions vary as to the credibility of cumulative case studies for answering program implementation and effects questions. One authority notes that publication biases may favor programs that seem to work, which could lead to a misleading positive view (Berger, 1983). Others raise concerns about problems in verifying the quality of the original data and analyses (Yin, 1989).
As a distinct approach to research, use of the case study originated only in the early 20th century.
The popularity of case studies as research tools has developed only in recent decades.
The case study offers a method of learning about a complex instance through extensive description and contextual analysis. The product articulates why the instance occurred as it did, and what one might usefully explore in similar situations.
Case studies can generate a great deal of data that may defy straightforward analysis. For details on conducting a case study, especially with regard to data collection and analysis, see the references listed below.
- Berger, Michael A. "Studying Enrollment Decline (and Other Timely Issues) via the Case Survey." Educational Evaluation and Policy Analysis, 5:3 (1983), 307-317.
- Datta, Lois-ellin (1990). Case Study Evaluations. Washington, DC: U.S. General Accounting Office, Transfer paper 10.1.9.
- Miles, Matthew B., and Huberman, A.M. (1984). Qualitative Data Analysis: A Sourcebook of New Methods. Beverly Hills, CA: Sage.
- Yin, Robert K. (1989). Case Study Research: Design and Methods. Beverly Hills, CA: Sage.
See also statistical study, statistics, scientific method, qualitative psychological research