Deciding whether a case study or a single case study design is the best to use in research depends utterly on what type of results and findings your trying to find out. Single-subject designs are most often used in psychology and are sensitive towards individual differences unlike group case studies, which are more sensitive to the averages of groups. In single-subject designs each participant serves as his or her own control, which is similar to a time-series design.
Single case studies use a continuous assessment therefore the behavior of the individual is observed repeatedly over time. This insures that any treatment effects or changes that occur to the individual are a result of the treatment over time. Where case studies often test two different groups and compare the differences before and after the treatments.
McMillan (2004) summarized five characteristics of single-subject research. It is key that it’s a reliable measure as it involves multiple measures. Also conditions such as time of day and location should be kept constant over measures, especially for before and after treatments. Also as the same measure is repeated over and over again it is vital that it’s a repeated measurement. Repeated measurements ensure a clear pattern of consistency in the behavior over time. McMillan also added that descriptions of conditions should be detailed in description. He also added that baseline and treatment conditions were important. The baseline behavior provides ‘the frame of reference which future behavior is compared’. It’s important to do follow the single-variable rule with a single subject design.
Where the pros of a single case study are mentioned above case studies have advantages of their own. From a good case study in psychology it’s possible for the development of hypotheses for later testing and a case study can provide detailed descriptions of specific cases. Although saying this, case studies in psychology can often be hard draw a cause and effect relationships or test hypotheses.
Therefore I believe the use of case study or a single-case study depends on what type of data is collected (qualitative or quantitative) and what conclusion the researcher is trying to reach.
McMillan, J. H. (2004). Educational Research: Fundamentals for the Consumer, 4th Edition. Allyn and Bacon: Boston.