Modest Advice in Selecting Case Study Designs

Now that you know how to define case study designs and are prepared to carry out design work, three pieces of advice may be offered.

1. Single- or Multiple-Case Designs?

The first word of advice is that, although all designs can lead to successful case studies, when you have the choice (and resources), multiple-case designs may be preferred over single-case designs. Even if you can do a “two-case”
case study, your chances of doing a good case study will be better than using a single-case design. Single-case designs are vulnerable if only because you will have put “all your eggs in one basket.” More important, the analytic ben­efits from having two (or more) cases may be substantial.

To begin with, even with two cases, you have the possibility of direct replica­tion. Analytic conclusions independently arising from two cases, as with two experiments, will be more powerful than those coming from a single case (or single experiment) alone. Alternatively you may have deliberately selected your two cases because they offered contrasting situations, and you were not seeking a direct replication. In this design, if the subsequent findings support the hypoth­esized contrast, the results represent a strong start toward theoretical replica­tion—again vastly strengthening your findings compared to those from a single case alone (e.g., Eilbert & Lafronza, 2005; Hanna, 2005; also see BOX 12).

BOX 12

Two, “Two-Case” Case Studies

12A. Contrasting Cases for Community Building

Chaskin (2001) used two case studies to illustrate contrasting strategies for capacity building at the neighborhood level. The author’s overall conceptual framework, which was the main topic of inquiry, claimed that there could be two approaches to building community capacity—using a collaborative organization to (a) reinforce existing networks of community organizations or (b) initiate a new organization in the neighborhood. After thoroughly airing the framework on theoretical grounds, the author presents the two case studies, showing the viability of each approach.

12B. Contrasting Strategies for Educational Accountability

In a directly complementary manner, Elmore, Abelmann, and Fuhrman (1997) chose two case studies to illustrate contrasting strategies for designing and imple­menting educational accountability (i.e., holding schools accountable for the aca­demic performance of their students). One case represented a lower cost, basic version of an accountability system. The other represented a higher cost, more complex version.

In general, criticisms about single-case studies usually reflect fears about the uniqueness or artifactual conditions surrounding the case (e.g., special access to a key informant). As a result, the criticisms may turn into skepticism about your ability to do empirical work beyond having done a single-case
study. Having two cases can begin to blunt such criticism and skepticism. Having more than two cases will produce an even stronger effect. In the face of these benefits, having at least two cases should be your goal. If you do use a single-case design, you should be prepared to make an extremely strong argument in justifying your choice for the case.

EXERCISE 2.5 Establishing the Rationale for a Multiple-Case Study

Develop some preliminary ideas about a “case” for your case study. Alternatively, focus on one of the single-case studies presented in the BOXES in this book. In either situation, now think of a companion “case” that might augment the single case. In what ways might the companion case’s findings supplement those of the first case? Could the data from the second case fill a gap left by the first case or respond better to some obvious shortcoming or criticism of the first case? Would the two cases together comprise a stronger case study? Could yet a third case make the findings even more compelling?

2. Closed Designs or Flexible Designs?

Another word of advice is that, despite this chapter’s details about design choices, you should not think that a case study’s design cannot be modified by new information or discovery during data collection. Such revelations can be enormously important, leading to your altering or modifying your original design.

As examples, in a single-case study, what was thought to be a critical or unique case might have turned out not to be so, after initial data collection had started; ditto a multiple-case study, where what was thought to be parallel cases for literal replication turn out not to be so. With these revelations, you have every right to conclude that your initial design needs to be modified. However, you should undertake any alterations only given a serious caution. The caution is to understand precisely the nature of the alteration: Are you merely selecting different cases, or are you also changing your original theo­retical concerns and objectives? The point is that the needed flexibility should not lessen the rigor with which case study procedures are followed.

3. Mixed Methods Designs: Mixing Case Studies with Other Methods?

Researchers have given increasing attention to “mixed methods research”— a “class of research where the researcher mixes or combines quantitative and qualitative research techniques, methods, approaches, concepts or language into a single study” (Johnson & Onwuegbuzie, 2004, p. 17, emphasis added). Confinement to a single study forces the methods being mixed into an integrated mode. The mode differs from the conventional situation whereby different methods are used in separate studies that may later be synthesized.

Mixed methods research forces the methods to share the same research questions, to collect complementary data, and to conduct counterpart analy­ses (e.g., Yin, 2006b)—in short, to follow a mixed methods design. As such, mixed methods research can permit investigators to address more complicated research questions and collect a richer and stronger array of evidence than can be accomplished by any single method alone. Depending upon the nature of your research questions and your ability to use different methods, mixed meth­ods research opens a class of research designs that deserve your consideration.

The earlier discussion of embedded case study designs in fact points to the fact that certain kinds of case studies already represent a form of mixed meth­ods research. The embedded case studies rely on more holistic data collection strategies for studying the main case but then call upon surveys or other more quantitative techniques to collect data about the embedded unit(s) of analysis. In this situation, other research methods are embedded within your case study.

The opposite relationship also can occur. Your case study may be part of a larger, mixed methods study. The main investigation may rely on a survey or other quantitative techniques, and your case study may help to investigate the conditions within one of the entities being surveyed. The contrasting relation­ships (survey within case or case within survey) are illustrated in Figure 2.6.

At the same time, mixed methods research need not include the use of the case study strategy at all. For instance, much historical work embraces the quantitative analysis of archival records, such as newspapers and other file material. And, in an even broader sense, mixed methods research need not be limited to combinations of quantitative and qualitative methods. For instance, a study could employ a survey to describe certain conditions, complemented by an experiment that tried to manipulate some of those conditions (e.g., Berends & Garet, 2002).

By definition, studies using mixed methods research are more difficult to execute than studies limited to single methods. However, mixed methods research can enable you to address broader or more complicated research questions than case studies alone. As a result, mixing case studies with other methods should be among the possibilities meriting your consideration.

Source: Yin K Robert (2008), Case Study Research Designs and Methods, SAGE Publications, Inc; 4th edition.