Case study is often defined in different ways, reflecting evolving practice. What is important then is to define the concept for yourself, and explain to your audience how you are using the term.
- A research approach in which one or few instances of a phenomenon are studied in depth (Given, 2008).
- An empirical inquiry that investigates a contemporary phenomenon within its real-life context; when the boundaries between phenomenon and context are not clearly evident; and in which multiple sources of evidence are used. (Yin, 1984)
Case study involves a detailed in depth analysis of an organisation, person, a group, an event, allowing an understanding of complex phenomena, such as organisations. A case study generally involves looking at a single case (which already exists), an object of study which is easily identified and separated (a bounded system) from other similar objects e.g. an organization, a place, an illness in one patient. Case study is a useful methodology for focussing on relationships connecting everyday practices in natural settings, placing attention on a local situation (Stake, 2006).
The case study is useful to investigate an issue in depth and ‘provide an explanation that can cope with the complexity and subtlety of real of life situation’ (Denscombe, 2010, p55).
Research questions revolve around ‘How?’ or ‘Why?’ and may be explanatory, exploratory or descriptive in nature (Yin, 2003).
Case study can be used to develop theory. Yin (2003, p 1) notes that a case study is a way to ‘contribute to our knowledge of individual, group, organisational, social, political and related phenomena’ Case study can be used to test theory : what is it supposed to do and does it do that? Case studies can be used to trace a process, developing an understanding and then test it (Bennett, Andrew)
Data collection 
Case studies generally use a combination of data collection methods.
Multiple case studies 
In multiple cases, research single cases are meaningful in relation to the other cases cited. Multiple case study research needs to use cases that are similar in some ways. The cases become "members of a group or examples of a phenomenon" (Stake, 2006, p. 6). This allows examination of what is similar and dissimilar about the cases. The researcher is looking for patterns and uniqueness, particulars and generalisations in the cases developed.
References and resources 
Denscombe,Martyn (2010)(4th ed). The good research guide for small scale social research projects. Maidenhead: Open University Pres McGraw Hill
Dufour, S. & Foutin, V., ‘Annotated bibliography of case study method’, Current Sociology vol.40/1, 1992, pp.166-181.
Fidel, R. (1984). ‘The Case Study Method: A Case Study’, Library and Information Science Research vol.6/3, pp.273-288.
Garson, G.D. (2008). Case Studies, available from http://faculty.chass.ncsu.edu/garson/PA765/cases.htm
Gerring, J. (2007). Case Study Research: Principles and Practices, Cambridge University Press, Cambridge.
Gilbertson, D. W. & Stone, R. J. (1985) (2nd ed). Human resources management: cases and readings. Sydney : McGraw-Hill, 1985.
Giving, L. M. (2008) (ed.), The SAGE Encyclopedia of Qualitative Research Methods, Los Angeles: Sage.
Hossain, Dewan Mahboob (2009). 'Case Study Research' Social Science Research Network http://ssrn.com/abstract=1444863
Marshall, C. & Rossman, G.B. (2006) (4th ed). Designing qualitative research, Thousand Oaks: Sage.
Merriam S. (1998). Qualitative research and case study application in education. San Francisco: Jossey Bass.
Ragin, C.C. & Becker, H.S. (1992), What is a Case? Exploring the foundations of social enquiry, Cambridge University Press, Cambridge.
Sadler, D. Royce (1985). ‘Evaluation, Policy Analysis and Multiple Case Studies: Aspects of focus and sampling’, Educational Evaluation and Policy Analysis, vol.7/2, pp.143-149.
Simons (2009). Case study research in practice. London: Sage
Stake, R. E. (1995). The art of case study research. Thousand Oaks: Sage Publications.
Stake, R.E. (2006), Multiple Case Study Analysis, New York & London: The Guildford Press.
Soy, Susan K. (1997). The case study as a research method. Available from http://www.ischool.utexas.edu/~ssoy/usesusers/l391d1b.htm
Stoecker, R., ‘Evaluating and rethinking the case study’, The Sociological Review vol.39, no.1, February 1991, pp.88-112.
Yin, R.K. (1989). ‘Case study research design and method’. Applied Social Research Methods Series 5. Newbury Park: Sage
Young, Raymond (2010). Case study research http://ise.canberra.edu.au/raymond/?s=case+study
Zach, L. (2006), ‘Using multiple case studies design to investigate the information-seeking behaviour of arts administrators’, Library Trends vol.55/1, pp.4-21.
See also 
- Topic:Business case studies
- Portal:Social entrepreneurship/Case Studies/more
- Wikiversity:Case studies
- CisLunarFreighter/Scripts and case studies
- Case studies in patent litigation
- Portal:Social entrepreneurship/Case Studies
- Evidence-based medicine/Case studies
- Case study: Blended design and openness
- Case study in psychology