Scope
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.
Types
Illustrative
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
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
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
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
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
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).
History
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.
Conclusions
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.
References
- 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.
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