Our discussion has progressed without a formal definition of case studies. Moreover, commonly asked questions about case studies still have been unanswered. For example, is it still a case study when more than one case is included in the same study? Do case studies preclude the use of quantitative evidence? Can case studies be used to do evaluations? Let us now attempt to define the case study strategy and answer these questions.
1. Definition of the Case Study as a Research Method
The most frequently encountered definitions of case studies have merely repeated the types of topics to which case studies have been applied. For example, in the words of one observer,
The essence of a case study, the central tendency among all types of case study, is that it tries to illuminate a decision or set of decisions: why they were taken, how they were implemented, and with what result. (Schramm, 1971, emphasis added)
This definition thus cites cases of “decisions” as the major focus of case studies. Other common cases include “individuals,” “organizations,” “processes,” “programs,” “neighborhoods,” “institutions,” and even “events.” However, citing a case topic4 is surely insufficient to establish the needed definition of case studies as a research method.
Alternatively, many of the earlier social science textbooks failed to consider the case study a formal research method at all (the major exception is the book by five statisticians from Harvard University—Hoaglin et al., 1982). As discussed previously, one common flaw was to consider the case study as the exploratory stage of some other type of research method, and the case study itself was only mentioned in a line or two of text.
Another definitional flaw has been to confuse case studies with ethnographies or with participant-observation, so that a textbook’s presumed discussion of case studies was in reality a description either of the ethnographic method or of participant-observation as a data collection technique. Many earlier methodological texts (e.g., see L. Kidder & Judd, 1986; Nachmias & Nachmias, 1992), in fact, only covered “fieldwork” as a data collection technique and omitted any further discussion of case studies.
In a historical overview of the case study in American methodological thought, Jennifer Platt (1992) explains the reasons for these treatments. She traces the practice of doing case studies back to the conduct of life histories, the work of the Chicago school of sociology, and casework in social work. She then shows how “participant-observation” emerged as a data collection technique, leaving the further definition of any distinctive case study method in suspension. Finally, she explains how the first edition of this book (1984) definitively dissociated the case study strategy from the limited perspective of only doing participant-observation (or any type of fieldwork). The case study strategy, in her words, begins with “a logic of design … a strategy to be preferred when circumstances and research problems are appropriate rather than an ideological commitment to be followed whatever the circumstances” (Platt, 1992, p. 46).
And just what is this logic of design? The critical features had been worked out prior to the first edition of this book (Yin, 1981a, 1981b) but now may be restated as part of a twofold, technical definition of case studies. The first part begins with the scope of a case study:
- A case study is an empirical inquiry that
- investigates a contemporary phenomenon in depth and within its real-life context, especially when
- the boundaries between phenomenon and context are not clearly evident.
In other words, you would use the case study method because you wanted to understand a real-life phenomenon in depth, but such understanding encompassed important contextual conditions—because they were highly pertinent to your phenomenon of study (e.g., Yin & Davis, 2007). This first part of the logic of design therefore helps to continue to distinguish case studies from the other research methods that have been discussed.
An experiment, for instance, deliberately divorces a phenomenon from its context, attehcling to only a few variables (typically, the context is “controlled” by the laboratory environment). A history, by comparison, does deal with the entangled situation between phenomenon and context but usually with noncontemporary events. Finally, surveys can try to deal with phenomenon and context, but their ability to investigate the context is extremely limited. The survey designer, for instance, constantly struggles to limit the number of variables to be analyzed (and hence the number of questions that can be asked) to fall safely within the number of respondents who can be surveyed.
Second, because phenomenon and context are not always distinguishable in real-life situations, other technical characteristics, including data collection and data analysis strategies, now become the second part of our technical definition of case studies:
- The case study inquiry
- copes with the technically distinctive situation in which there will be many more variables of interest than data points, and as one result
- relies on multiple sources of evidence, with data needing to converge in a triangulating fashion, and as another result
- benefits from the prior development of theoretical propositions to guide data collection and analysis.
In essence, the twofold definition shows how case study research comprises an all-encompassing method—covering the logic of design, data collection techniques, and specific approaches to data analysis. In this sense, the case study is not limited to being a data collection tactic alone or even a design feature alone (Stoecker, 1991). How the method is practiced is the topic of this entire book.
EXERCISE 1.4 Finding and Analyzing an Existing Case Study from the Literature
Retrieve an example of case study research from the literature. The case study can be on any topic, but it must have used some empirical method and presented some empirical (qualitative or quantitative) data. Why is this a case study? What, if anything, is distinctive about the findings that could not be learned by using some other social science method focusing on the same topic?
Certain other features of the case study method are not critical for defining the method, but they may be considered variations within case study research and also provide answers to common questions.
2. Variations within Case Studies as a Research Method
Yes, case study research includes both single- and multiple-case studies. Though some fields, such as political science and public administration, have tried to distinguish between these two approaches (and have used such terms as the comparative case method as a distinctive form of multiple-case studies; see Agranoff & Radin, 1991; Dion, 1998; Lijphart, 1975), single- and multiple-case studies are in reality but two variants of case study designs (see Chapter 2 for more).
And yes, case studies can include, and even be limited to, quantitative evidence. In fact, any contrast between quantitative and qualitative evidence does not distinguish the various research methods. Note that, as analogous examples, some experiments (such as studies of perceptions) and some survey questions (such as those seeking categorical rather than numerical responses) rely on qualitative and not quantitative evidence. Likewise, historical research can include enormous amounts of quantitative evidence.
As a related but important note, the case study method is not just a form of “qualitative research,” even though it may be recognized among the array of qualitative research choices (e.g., Creswell, 2007). Some case study research goes beyond being a type of qualitative research, by using a mix of quantitative and qualitative evidence. In addition, case studies need not always include the direct and detailed observational evidence marked by other forms of “qualitative research.”
And yes, case studies have a distinctive place in evaluation research (see Cronbach & Associates, 1980; Patton, 2002; U.S. Government Accountability Office, 1990). There are at least four different applications. The most important is to explain the presumed causal links in real-life interventions that are too complex for the survey or experimental strategies. A second application is to describe an intervention and the real-life context in which it occurred. Third, case studies can illustrate certain topics within an evaluation, again in a descriptive mode. Fourth, the case study strategy may be used to enlighten those situations in which the intervention being evaluated has no clear, single set of outcomes. Whatever the application, one constant theme is that program sponsors—rather than research investigators alone—may have the prominent role in defining the evaluation questions and desired data categories (U.S. Government Accountability Office, 1990).
And finally, yes, case studies can be conducted and written with many different motives. These motives vary from the simple presentation of individual cases to the desire to arrive at broad generalizations based on case study evidence but without presenting any of the individual case studies separately (see BOX 3).
Multiple-Case Studies: Case Studies Containing Multiple “Cases”
Case studies can cover multiple cases and then draw a single set of “cross-case” conclusions. The two examples below both focused on a topic of continuing public interest: identifying successful programs to improve U.S. social conditions.
3A. A Cross-Case Analysis following the Presentation of Separate, Single Cases
Jonathan Crane (1998) edited a book that had nine social programs as separate cases. Each case had a different author and was presented in its own chapter. The programs had in common strong evidence of their effectiveness, but they varied widely in their focus—from education to nutrition to drug prevention to preschool programs to drug treatment for delinquent youths. The editor then presents a crossprogram analysis in a final chapter, attempting to draw generalizable conclusions that could apply to many other programs.
3B. A Book Whose Entire Text Is Devoted to the Multiple-Case (“Cross-Case”) Analysis
Lisbeth Schorr’s (1997) book is about major strategies for improving social conditions, illustrated by four policy topics: welfare reform, strengthening the child protection system, education reform, and transforming neighborhoods. The book continually refers to specific cases of successful programs, but these programs do not appear as separate, individual chapters. Also citing data from the literature, the author develops numerous generalizations based on the case studies, including the need for successful programs to be “results oriented.” Similarly, she identifies six other attributes of highly effective programs (also see BOX 41A and 41B, Chapter 6, p. 173).
EXERCISE 1.5 Defining Different Types of Case Studies Used for Research Purposes
Define the three types of case studies used for research (but not teaching) purposes: (a) explanatory or causal case studies, (b) descriptive case studies, and (c) exploratory case studies. Compare the situations in which these different types of case studies would be most applicable. Now name a case study that you would like to conduct. Would it be explanatory, descriptive, or exploratory? Why?
Source: Yin K Robert (2008), Case Study Research Designs and Methods, SAGE Publications, Inc; 4th edition.