Yin identifies four basic types of design for case studies. The four basic types of designs for case studies are (Yin, 2009, pp. 46-47):
1. Single case (holistic) designs. 2. Single case (embedded designs. 3. Multiple-case (holistic) designs. 4. Multiple-case (embedded) designs.
The major distinction between the two basic forms of case studies is that one is single case and the other is multi-case designs (Yin, 2009). There are several rationalizations for a single case study, they may include the following (Yin, 2009, pp. 47-49):
1. The case represents the critical case in testing a well-formulated theory. 2. The case represents an extreme or a unique case.
3. The case is the representative or typical case. 4. The case is the revelatory case.
5. The case is the longitudinal case: studying the same single case at two or more different points in time.
When the case represents the critical case, “the case is testing a well-formulated theory” where the case has propositions and circumstances that are clearly defined and a significant
contribution to knowledge and theory building exits (Yin, 2009, p. 47). For the extreme or
unique cases the rationale would be that the documentation and analysis of any such case goes
beyond what exists in the present (Yin, 2009). For the representative or typical case the rational is to “capture the circumstances and conditions of an everyday or common place situation” (Yin, 2009, p. 48). “For the revelatory case the rational is the researcher has an opportunity to observe and analyze a phenomenon previously inaccessible to social science inquiry” (Yin, 2009, p. 48). For the longitudinal case the rational “the theory of interest would likely specify how certain conditions change over time, and the desired time intervals would presumably reflect the anticipated stages at which the changes should reveal themselves” (Yin, 2009, p. 49). A “potential vulnerability of the single-case design is that a case may later turn out not to be the case it was thought to be at the outset” (Yin, 2009, pp. 49-50). Upfront planning to address major concerns will help mitigate this risk.
A full understanding of the holistic versus the embedded case studies is needed to understand the case; each has its advantages and disadvantages (Yin, 2009). An embedded case study design occurs when a single case attention focuses on a specific subunit(s) of the case (Yin, 2009, p. 50). An example may be if the case study was about a government organization
and then conclusions about employee demographics are presented. “A major one [pitfall] occurs when the case study focuses only on the subunit level and fails to return to the larger unit of analysis” (Yin, 2009, p. 52). Yin provides an example of this below:
An evaluation of a program consisting of multiple projects may include project characteristics as a subunit of analysis. The project-level data may even be highly quantitative if there are many projects. However, the original evaluation becomes a project study (i.e., a multiple-case study of different projects) if no investigating is done at the level of the original case – that is, the program. (Yin, 2009, p. 52)
A holistic case study design examines the “global nature of an organization or of a program” (Yin, 2009, p. 50). “The holistic design is advantageous when no logical subunits can be identified or when the relevant theory underlying the case study is itself of a holistic nature. Potential problems arise, however, when a global approach allows the investigator to avoid examining any specific phenomenon in operational detail. Thus a typical problem with the holistic design is that the entire case study may be conducted at an unduly abstract level, lacking sufficiently clear measures of data” (Yin, 2009, p. 50). Another problem with the holistic design is that “the entire nature of the case study may shift, unbeknownst to the researcher, during the course of the study” (Yin, 2009, p. 52).
A multiple-case study is one where more than one case study is performed during the study. Multiple case studies have distinct advantages in contrast to single case studies. “The evidence from multiple cases is often considered more compelling, and the overall study is therefore regarded as being more robust (Herriott and Firestone, 1983)” (Yin, 2009, p. 53). “By definition, the unusual or rare case, the critical case, and the revelatory case all are likely only
single cases” (Yin, 2009, p. 53). Multiple case studies are designed to show replication of issues not for the purpose of sampling the data; the methodology for these types of case study design is not the same. For multiple case studies “each case must be carefully selected so that it either (a) predicts similar results (a literal replication) or (b) predicts contrasting results but for
anticipatable reasons (a theoretical replication)” (Yin, 2009, p. 54).
“An important step in all of these replication procedures is the development of a rich, theoretical framework. The framework needs to state the conditions under which a particular phenomenon is likely to be found (a literal replication) as well as the conditions when it is not likely to be found (a theoretical replication). The theoretical framework later becomes the vehicle for generalizing to new cases, again similar to the role played in cross-experiment designs. Furthermore, just as with experimental science, if some of the empirical cases do not work as predicted, modification must be made to the theory. Remember, too, that theories can be practical and not just academic” (Yin, 2009, p. 54). The replication approach to multiple-case studies is shown in Figure 16 below:
Develop Theory Conduct 1st Case Study Select Cases Design Data Collection Protocol Conduct Remaining Case Study Reports Conduct 2nd Case Study Write Individual Case Report Write Individual Case Report Write cross- case Report Develop Policy Implications Modify Theory Draw cross- case conclusions Write Individual Case Report
Define and Design Prepare, Collect, Analyze Analyze and Conclude Figure 16: Case Study Method {Adapted from (Yin, 2009, p. 57)}
The case study method shown above is best described by Yin below (2009, p .56):
The figure indicates that the initial step in designing the study must consist of theory development, and then shows that case selection and the definition of specific measures are important steps in the design and data collection process. Each individual case study consists of a “whole” study, in which convergent evidence is sought regarding the facts and conclusions for the case; each case’s conclusions are then considered to be information needing replication by other individual cases. Both the individual cases and the multiple-case results can and should be the focus of a summary report. For each individual case, the report should indicate how and why a particular proposition was demonstrated (or not demonstrated). Across cases, the report should indicate the extent of
replication logic and why certain cases were predicted to have certain results, whereas other cases, if any, were predicted to have contrasting results.
Particular attention to the loop in the Figure 16 should be made by the researcher as this is the feedback loop that occurs after each case, signifying knowledge gained (Yin, 2009). This new insight may require a re-design (Yin, 2009). The need for replication is associated with the strength of the rival propositions (Yin, 2009, p. 58). The rational for multiple case studies derives from the researcher’s understanding of literal and theoretical replications (Yin, 2009). With the multiple case inquiry, prior knowledge allows the researcher to focus on the “how” and “why” of a case outcome (Yin, 2009, p. 59).
This section described the differences between single and multiple case study designs. An understanding of whether the case study is embedded or holistic occurs in the early design of the case study. The use of replication for multiple case studies requires attention to be given to the framework of analysis. This framework allows for the replication of the case study providing a higher level of validity sought by the researcher. The next section examines the preparation techniques for collection of case study data.