Case Units and Case Families

Case Units and Case Families

Learning Objectives

  • Consider the ways in which a classification scheme – a “case family” type – might help you situation your research in relation to other works in your field.
  • Look through the various “case families” shown in Figure 10 and observe their affiliation with single case or multi-case strategies.
  • Inspect the logic offered in Table 1 for each of these “case families,” and assess whether your own work might follow one of these rationales.
  • Reflect on the importance of maintaining commitment to the case unit throughout the research project, as well as the risks of veering off course.

From Case Units to “Case Families”

The previous module introduced students to several of the challenges involved in selecting a case unit (namely, decisions about object-versus-process and diachronic-versus-synchronic bounding). The question then arises: can case studies be assigned to “types” based on these decisions? Some methodologists believe the answer is “yes,” and have devised families of case study based on the myriad unit-structures and relationship between units (when multiple have been selected). See, for example, the five families proposed by Seawright and Gerring (2008) and the six families proposed by Brewer and Hunter (2006, pp. 82-88) for in-depth discussion. Thomas (2015) assembles several of these case family taxonomies into a macro-classification scheme. Figure 10 below offers a simplified outline of some of the more popular families, and Table 1 breaks down the logic for these families.  

  FIGURE 10: Families of Cases (Based on their Logic)


Pasted ImageTABLE 1: Types of Logic for Case Families 

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Commitment to the Case Unit(s)

 Readers will recall from Module 4 that the third most common problem when devising case units is the level of commitment on the part of the researcher. Baxter and Jack recount from their personal experience that novice researchers tend to veer from their case units in some phase of their study, creating issues with consistency (2008, pp. 546-47). Often the cause of this veering is the researcher’s desire to incorporate too many aspects of a phenomenon in a single study, pushing beyond the boundaries of what they defined as case(s). Novice researchers should question from the outset whether they can be satisfied with the narrow scope selected for the study, as well as the concise structuring of the case units. If the answer is “no,” then it might be time to contemplate a switch in research design, or a reevaluation of the study’s problem statement and purpose.

Evidence of veering takes many forms. Some researchers sample individuals who are not aligned to the narrow boundaries of the case units. Others collect “data” on attributes that fall outside the unit structure, risking extraneous information that fails to answer the research questions (technically this information is not true “data” because it fails to align). Still others create analytic categories that do not apply to the case units, assigning meaning based on outside considerations (perhaps a personal experience that did not mirror the case units selected). Whatever the evidence, the impact for the study is damaging: the veering produces a moving target that undermines the essential feature of the research design, and in so doing, challenges the consistency of data and analytic results reported. It is for this reason that Baxter and Jack implore their students “to consider what your case study will NOT be” (2008, p. 546).


Baxter, P., & Jack, S. (2008). Qualitative case study methodology: study design and implementation for novice researchers. The Qualitative Report 13 (4). Retrieved from:

 Brewer and Hunter. (2006). Foundations of Multimethod Research: Synthesizing Styles. Thousand Oaks: SAGE. 

 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.

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