Following from the concern of external validity, it is important to observe difference between various types of case that is often made by writers.
- The critical case: the hypothesis is specified clearly and the case is selected on the basis that it would allow a better comprehension of the circumstances in which the hypothesis might and might not hold.
- The unique case: this is basically a common focus in clinical studies.
- The revelatory case: it is important for the researcher here to have an opportunity to observe and analyse a phenomenon that was previously inaccessible to scientific investigation. The idea here is interesting to restrict with only previous studies but not considered necessary. Most of the qualitative case study research that is conducted with a predominantly inductive approach regards single case studies as basically ‘revelatory’.
- The representative or typical case: it seeks to work on everyday situations or form of organisation.
- The longitudinal case: what is considered important here that how a situation changes over time.
Any specific study can indulge into a combination of these elements which are considered and viewed as rationales for selecting particular cases.
Case study researchers argue that their objective is to produce an intensive examination of a single case, in relation to their involvement in a theoretical analysis. The main idea is the quality of the theoretical reasoning in which the researcher of case study is involved. Thus, case studies are associated with both bringing out new theory and its testing.