1 Descriptive (exploratory-descriptive, focused-descriptive)
2 Theoretical-heuristic (grounded theory building, hermeneutic work)
3 Theory-testing (testing propositions within grounded theory, metatheoretical construction). (Edwards 1998)
1 Holistic‘A holistic case study is shaped by a thoroughly qualitative approach that relies on narrative, phenomenological descriptions. Themes and hypotheses may be important but should remain subordinate to the understanding of the case.’
2 Embedded‘Embedded case studies involve more than one unit, or object, of analysis and usually are not limited to qualitative analysis alone.’ (Scholz and Tietje 2002, p. 9)
1 Intrinsic, ‘if the study is undertaken because, first and last, one wants better understanding of this particular case’;
2 Instrumental, ‘if a particular case is examined mainly to provide insight into an issue or to redraw a generalization’;
3 Multiple or collective, when ‘a number of cases may be studied jointly in order to investigate a phenomenon, population or general condition’. (Stake 2005, p. 445)
1 Typical
2 Diverse
3 Extreme
4 Deviant
5 Influential
6 Crucial
7 Pathway (i.e. chosen to elucidate causal mechanisms)
8 Most-similar
9 Most-different. (Gerring 2007, pp. 89–90)
1 Idiographic (inductive or theory-guided) –‘which aim to describe, explain or interpret a particular “case” and which can be either inductive or theory-guided’.
2 Hypothesis-generating
3 Hypothesis-testing
4 Plausibility probes (pilot or illustrative studies) –‘an intermediary step between hypothesis generation and hypothesis testing and which include “illustrative” case studies’. (Levy 2008, p. 3)
1 Explanatory or causal
2 Descriptive
3 Exploratory
All of which may be single or multiple. (Yin 2009, pp. 19–21)
1 Subject ‘the case itself’ and object ‘the analytical frame or theory through which the subject is viewed and which the subject explicates’
2 Purposes and approach – theory-centred or illustrative
3 Comparative/non-comparative – employment of time. (Thomas 2011c, p. 511)
The classifications are all fairly simple, most involving no more than two, three, four or five categories, though Gerring’s includes nine. Some, however, then break the categories down further in another hierarchical level, or identify a series of dimensions or spectra along which the characteristics of case studies vary.
Thomas’s classification is probably the most complex, as it involves at least three distinctions: whether the focus is on the subject (the case itself) or the object (the theoretical framework adopted), whether the case study is theory-centred or illustrative, and whether a comparative or non-comparative approach is adopted. The last two of these distinctions are common to, though differently expressed in, many of the typologies.
The comparative/non-comparative distinction concerns whether the focus of the study is on a single case or more than one case (a point highlighted in their definitions of case study by Gillham and Swanborn: see Box 2.1). Cunningham also refers to this distinction as comparative, while both Stake and Yin use the alternative terms ‘multiple’ or ‘collective’, while for Scholz and Tietje this element is wrapped up in their ‘embedded’ category.
Levy, following Eckstein, offers ‘plausibility probes’ as one type of case study, by which is meant what is now more commonly termed a pilot study. This obviously has overlaps with the single/multiple case study distinction, as it implies that more cases will then be selected for study once the pilot study has been completed, and lessons have been learnt from it.
Whether or not the focus of the case study is on theory is also a key concern. A focus on theory is conveyed by Eckstein in his ‘disciplined-configurative’ type, by Cunningham in the term ‘intensive’, by Edwards in the ‘theoretical-heuristic’ and ‘theory-testing’ distinctions, by Levy in the ‘idiographic’ type (and also, to an extent, in the ‘hypothesis-generating’ and ‘hypothesis-testing’ types), and by Yin in his ‘explanatory or causal’ category.
Alternatively, a focus which is explicitly not on theory is classified by both Edwards and Yin as ‘descriptive’, and by Eckstein as ‘configurative-idiographic’.
Other elements are emphasised in their classifications by just one of the authors included. For Scholz and Tietje, the holistic/embedded distinction is partly about the use of qualitative and/or quantitative methods. Cunningham links case study to another research design when he uses ‘action research’ as one of his categories (this linkage is further discussed and exemplified in Chapter 6). Edwards brings in a further research design when he links both of his ‘theoretical-heuristic’ and ‘theory-testing’ categories to grounded theory (which is also discussed in Chapter 6). Gerring’s classification is unusual in emphasising the relation of the case to the population from which it is chosen.
Other distinctions do not appear in any of the eight classifications considered here. The most notable of these is probably the distinction between teaching and research case studies, which is discussed in the next section.
It is worth mentioning here the contributions to this discussion of another two authors. First, Mitchell (1984, p. 239) introduces a typical/telling case dichotomy (cf. Gerring’s use of typical and influential) in this context:
A good case study… enables the analyst to establish theoretically valid connections between events and phenomena which previously were ineluctable. From this point of view, the search for a ‘typical’ case for analytical exposition is likely to be less fruitful than the search for a ‘telling’ case, in which the particular circumstances surrounding a case serve to make previously obscure theoretical relationships suddenly apparent.
Second, Simons (2009, pp. 21–22), after noting Stake’s distinction between intrinsic, instrumental and collective cases, and the theory-led or theory-generated categorisation, also draws attention to evaluation and ethnographic case studies. These last two categories reflect, on the one hand, the purposes to which case study research is often put, and on the other hand, particular traditions of case study research (both of which are discussed in more detail in Chapter 6).
While none of the nine typologies seems entirely satisfactory, therefore, and their use of alternative terms to mean the same thing (or, at least, much the same thing) is confusing, this analysis suggests that there are three major factors to bear in mind when considering examples of case studies:
Whether they focus on a single case or involve a comparative study of two or more cases.
Whether they confine themselves to description or engage with theory.
Whether they are intended primarily to support teaching or research.
While the third of these factors is discussed next, the first two are considered in more detail in Chapter 8.
Teaching and Research Case Studies
In