Epistemic Issues, Part 1: The “Case Unit”

Epistemic Issues, Part 1: The “Case Unit”

Learning Objectives

  • Take a moment to think about the importance of deciding early on what will define the “case unit.”
  • Look over the three areas of case unit selection that tend to give novice researchers the greatest difficulty. 
  • Make a note of the difference between the “case unit” and the “phenomenon of interest” in case research, given the frequent confusion on this subject.


The Importance of Units

We learned in Module 2 that even in the earliest case studies, Le Play assigned case units to frame his investigations of social stability in working class communities. From the very beginning, then, the hallmark feature of the case study has been the selection of a real-world framework from which to observe the phenomenon in its natural system. This structural unit, while meaningless in itself, allows the researcher to anchor his or her observations to a common context, and ultimately use these observations to construct meaning. Robert Stake argued – against Yin – that the selection of case units holds priority in research even when difficult methodological choices seem pressing (such as whether to pursue qualitative versus “mixed” data sources), because the researcher first has to identify what will be analyzed for meaning. Fundamentally, “the case study is not a methodological choice but a choice of what is to be studied” (2005, p. 443). So, students should start by decided which real-world aspects to scrutinize in the form of a complex unit, and only afterward turn their attention to methodological considerations. Stake is hardly alone in this opinion. Renowned sociologist Michel Wieviorka agrees that “for a ‘case’ to exist, we must be able to identify a characteristic unit” and have “the means of interpreting it or placing it in a context. It is significant only if an observer can refer it to an analytical category or theory” (1992, p. 160). Thus, the unit is not some arbitrary compartment; it is a unit of analysis


Choosing a case unit is no easy task, to be sure. Baxter and Jack found in their review of the literature that unit selection has proven “a challenge for both novice and seasoned researchers alike” (2008, p. 545). Module 4 outlines three of the common reasons that students often struggle with case unit selection, and then reviews the first of these in greater detail (the second and third are discussed in subsequent modules).  


FIGURE 7: Reasons for Case Unit Issues


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Defining the Case Unit

Methodologist Charles Ragin observes that “the biggest obstacle to clear thinking about ‘What is a case?’ is the simple fact that the term ‘case’ is used in so many different ways,” and has been for over a hundred years now (see Module 2). The word is variously “used to refer to data categories, theoretical categories, historically specific categories, substantive categories, and so on,” leaving a researcher unable to “reconcile the varied approaches to the question of cases” (1992, p. 217). There is no consensus on what is meant by “case”; only a series of family resemblances cobbled together by methodological authorities. Seawright and Gerring (2008), for example, propose families such as “typical case,” “diverse case,” “extreme case,” “deviant case,” and “influential case” (detailed further in Module 6). Given the lack of consensus in this debate, the best advice for students is to develop a clear definition and rationale for the unit(s), and maintain consistency through their study, so that others can follow their logic.


Broadly speaking, a “case unit” is an instance of a given phenomenon as it occurs in a real-world system. It exhibits boundaries of both space and time and is best analogized to a “window” or “snapshot” in that it allows the researcher to observe a phenomenon from a specific angle or context (Blejenbergh, 2010; Stake, 1995; Ragin, 1992). To say anything more about the “case” risks unduly narrowing the researcher’s scope or creating confusion. For example, when Stake claims (1995, p. 2) that all cases should be “integrated systems” in themselves (rather than simply occurring in a system), he prompts the reader to wonder: does he exclude artifacts such as photographs or publications? Does he exclude individual people? Does he exclude cultures? Does he exclude social or behavioral processes? Merriam thought that Stake had been too restrictive in his definition and proposed a more liberal meaning in her own account (1998, p. 27). She felt that as long as the researcher could “fence-in” the phenomenon by installing boundaries and context, the term “case unit” could be applied. 


Another common source of confusion is the methodologists’ tendency to conflate the “case unit” with the phenomenon itself. The most well-known example occurs in Miles and Huberman’s (1994) classic text, where the authors ask the readers to “define the case as a phenomenon of some sort occurring in a bounded context” (p. 25). Merriam embraces this notion as well, conceiving the case study as “an intensive, holistic description and analysis of a bounded phenomenon such as a program, an institution, a person, a process, or a social unit” (1998, xiii). Yin likewise refers to the case as “a contemporary phenomenon within its real-life context, especially when the boundaries between a phenomenon and context are not clear […]” (2002, p. 13). The whole point of the case method, however, is to gain a multi-dimensional perspective of a social phenomenon. To suggest that a case unit is nothing more than the “phenomenon in its real-life context” is disingenuous because, from the start, the researcher has to make a conscious decision about how to carve-up the “real life context.” As a matter of practice, therefore, the case is distinct from the phenomenon under study (Gomm, Hammersley, & Foster, 2000[b], p. 102). Fletcher and Plakoyiannaki clarify that while “the case unit of analysis is the major entity being analyzed in the study,” it should “not to be confused with the […] empirical unit,” which is commonly called the phenomenon (2010, pp. 838-39, italics added).


Figure 8: illustrates the anatomy of a single case study (on the left side) and multi-case study (on the right side) in simplistic fashion. While the single case scenario is straight forward, the multi-case requires a bit of clarification. Even before the researcher compares across cases – searching for previously unknown similarities or differences – there are known commonalities that bind the cases to a mutual phenomenon. These commonalities are what Stake calls a “quintain” (2006). They ensure that when looking at even the most highly varied cases, there is still a common denominator.  



 FIGURE 8: Anatomy of a Case Study (Simplistic) 


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 Baxter, P., & Jack, S. (2008). Qualitative case study methodology: study design and implementation for novice researchers. The Qualitative Report 13 (4). Retrieved from: http://nsuworks.nova.edu/tqr/vol13/iss4/2/

 Bleijenbergh, I. (2010). Case selection. In A. J. Mills, G. Durepos, & E. Weibe (Eds.), Encyclopedia of Case Study Research, Vol. 1 (pp. 61-63). London: SAGE.

 Fletcher, M., & Plakoyiannaki, E. (2010). Sampling. In A. J. Mills, G. Durepos, & E. Weibe (Eds.), Encyclopedia of Case Study Research, Vol. 1 (pp. 838-39). London: SAGE.

 Gomm, R., Hammersley, M., & Foster, P. (2000[b]). Case study and generalization. In R. Gomm, M. Hammersley, & P. Foster (Eds.), Case Study Methods (pp. 98-116). Thousand Oaks: SAGE.

 Merriam, S. B. (1998). Qualitative Research and Case Study Applications in Education. San Francisco: Jossey-Bass.

 Miles, M. B., & Huberman, A. M. (1994). Qualitative Data Analysis (2nd ed.). Thousand Oaks: SAGE.

 Ragin, C. C. (1992). “Casing” and the process of social inquiry. In C. C. Ragin & H. S. Becker (Eds.), What is a Case? Exploring the Foundations of Social Inquiry (pp. 217-27). Cambridge, UK: Cambridge Univ. Press.

 Seawright, J., & Gerring, J. (2008). Case selection techniques in case study research: a menu of qualitative and quantitative options. Political Research Quarterly 61 (2): 294-308.

 Stake, R. E. (1995). The Art of Case Study Research. Thousand Oaks: SAGE.

 Stake, R. E. (2005). Qualitative case study. In N. K. Denzin & Y. S. Lincoln (Eds.), The SAGE Handbook of Qualitative Research (3rd ed., pp. 443-66). Thousand Oaks: SAGE.

 Stake, R. E. (2006). Multiple Case Study Analysis. New York: Guilford.

 Wieviorka, M. (1992). Case studies: history or sociology? In C. C. Ragin & H. S. Becker (Eds.), What is a Case? Exploring the Foundations of Social Inquiry (pp. 159-72). Cambridge, UK: Cambridge Univ. Press.

 Yin, R. K. (2002). Case Study Research: Design and Methods (3rd ed.). Thousand Oaks: SAGE.

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