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How to... undertake case study research

Options:     Print Version - How to...  undertake case study research, part 2 Print view

Design issues

What is research design?

A research design is a plan for getting from your original question or hypothesis to obtaining workable results from your research, on which you can base defensible conclusions.

Good case study design involves providing empirical data for analysis and conclusion (Gummesson, 2007), but doing so in such a way that stands up to scrutiny.

Defining the research

The first task is to decide what it is you are trying to find out by defining your research question. Carrying out a literature review is an essential precursor to most research, and is a good way of getting ideas for research questions.

The questions need to be suitable: large enough to provide sufficient scope for research, but new enough not to have already been answered.

Yin (2009, location no. 827) advises narrowing down the research question to something more specific, in order to look for relevant evidence. This may take the form of a proposition.

The role of theory

There is some debate as to whether or not it is appropriate to use theory at this stage, but some initial delving into theory will help you further define the parameters of the case you are investigating.

Note too that it is important to understand your own ontological and epistemological perspective: are you carrying out interpretive or positivist research? Broadly speaking, the positivist approach looks at objective reality, which exists beyond the human mind, whereas the interpretivist approach sees knowledge of the world as inevitably affected by the observer.

Practical considerations

When considering your theoretical position at the outset, it is important not to lose sight of an important practical consideration: will the case you have chosen (or are considering choosing) cooperate with your research? You need a case where people will be helpful, leading you to key informants, providing access to documents, and allowing you to interview or survey staff. For example, a school might illustrate an important theoretical point, but if teachers and pupils refuse to engage and you can't gain access to classrooms, it will not be of much use.

Unit of analysis

The beginning of the research process is all about definition: not only your research question, but also your unit of analysis, which is the actual object or entity being studied. Also, the unit must be at the same level as the object of the proposition (Gerring and McDermott, 2007). For example, a company or business could be the unit of analysis, and the object of the proposition be to examine company performance.

On the other hand, your unit of analysis might be an individual or a small group, for example if you were looking at the effects of a particular social intervention such as whether or not neighbourhood policing could reduce crime. It could even be something less tangible, such as a community, a decision, a project, or even a book marketing campaign.

Population and sampling in case selection

Population – the group of people or the area you are investigating – and the sample (the subset of the population you are studying) are both important research principles (see Sampling techniques). Both apply in case study research.

Seawright and Gerring (2008, pp. 295-296) claim that the selection of cases has the same objectives as random sampling in that what is desired is a representative sample and useful variation on the dimensions of theoretical interest. However, given the difficulties of getting a representative case, on both practical and theoretical grounds, they suggest that purposive sampling may be more appropriate (p. 296).

Developing the instrument – different case designs

The work of defining the research questions and proposition is unique to each study, but when it comes to selecting and developing the instrument, there are a number of different possible research designs for case studies.

Single vs multiple case design

This simply means choosing whether your study will include just one, or several cases.

Both types of case study design have their advantages.

Yin (2009, location no. 1201) lists five rationales for single cases:

  1. A critical case – i.e. one that can test a particular theory.
  2. An extreme or unique case – for example, a study of a rare disorder.
  3. A representative case – a case that is representative, or typical, of a particular situation.
  4. A revelatory case – one that reveals a phenomenon hitherto unexplored.
  5. A longitudinal case – a study of changes over time.

The big advantage of multiple case studies is that evidence is provided from many sources, thus making it easier to generalize. A single case, on the other hand, may be considered idiosyncratic. The use of multiple case designs has therefore become more frequent over recent years.

Another advantage of multiple case design is the methodological similarity with the experiment. This has been pointed out by a number of authors – Gerring and McDermott (2007), Lloyd-Jones (2003) and Yin (2009) – despite the fact that the case study is normally considered a qualitative method.

Its disadvantage, however, is its resource intensiveness.

Holistic vs embedded

Single cases and multiple cases can be holistic or embedded. A holistic case is one where the case is the unit of analysis; an embedded one is where there are several units of analysis in the case. This can be represented by Table I.

Table I. Matrix depicting single and multiple holistic cases versus single and multiple embedded cases
One case with one unit of analysis
Several cases each with one unit of analysis
One case with several units of analysis
Several cases each with several units of analysis

For example, a case could be about a school and its response to a new demographic trend or government edict, in which case it would be holistic. If within the school, several different classes were studied, then these sub-units, or "mini cases", would be embedded within the overall case.

Combining the case method with other methods

Some researchers combine case studies with other methods, such as a survey: for example, you could conduct a survey of several local councils, and provide a case study of one council. This type of approach has the benefit of combining qualitative and quantitative research.

Hitherto it has been assumed that theory is developed as part of the initial research work, drawing from the literature review, and that data are analysed against theory. However, with grounded theory design, the opposite happens: data are collected first of all, then theory developed, then more data are collected and compared with the theory, so the whole becomes an iterative process (see How to... implement grounded theory).

The iterative quality of grounded theory would seem to remove it from consideration in orthodox case study design.

Quality in case study research

All research needs to conform to the following quality criteria:

1. Construct validity – this is all about making sure the research uses the right operational measures, appropriate to what is being studied. Construct validity can be improved by:

  • Multiple sources of evidence, i.e. data collection methods, which can be triangulated against one another.
  • Having a chain of evidence.
  • Letting key informants review the draft (Yin, 2009, location no. 1110).

2. Internal validity – this seeks to establish a causal relationship, and is relevant for explanatory rather than exploratory cases. The researcher needs to establish that x causes y, and show that there are no other factors that could have played a part in y.

3. External validity – the extent to which it is possible to generalize from the findings of case studies. Many would say that it is not, on the grounds that case studies are too particular (although this applies less to multiple case studies).

Surveys, based on a sample of a larger population, allow for statistical generalization. Case studies, on the other hand, can offer results which can be generalized against a particular theory. This is known as analytical generalization.

4. Reliability – another researcher should be able to go in and repeat the case study, and come up with the same findings. (Note that this is different from being able to replicate the results in another case.) The way to make this possible is by documenting the procedures in the research.

Using case studies to generate theory

Cepeda and Martin (2005) see theory building as a key stage in the case study research process. After the collection of data, there is a stage for reflection, which enables the researcher to update the initial conceptual framework on which the research was based. The result is a cyclical process of theory, producing a research process giving rise to data from which fresh theory can be formulated, and fresh research carried out. Because research takes place "in the field", there is a close relationship between theory and what is happening on the ground.

Figure 1. Cepeda and Martin's view of conceptual frameworks and the research cycle (2005, p. 861).

Figure 1. Cepeda and Martin's view of conceptual frameworks and the research cycle (2005, p. 861)

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