Page 169 -

156 CHAPTER 7 Case studies

distinguishing between similar items (such as CDs); and the need for flexibility
and interoperability.
Although Sara does not provide a comprehensive picture of the needs and con-
cerns of blind people, the investigations of her needs and goals led to valuable in-
sights that might apply to many other blind people.
The remainder of this chapter uses this specific case study to develop a broader
understanding of case studies in general.

7.3 WHAT IS A CASE STUDY?
A case study is a detailed examination of one or more specific situations. The case
study described above helped the researchers to understand how Sara used a variety of
technologies to accomplish multiple tasks. They were specifically interested in under-
standing “what technologies were most valued and used, when they were used and for
what purpose” (Shinohara and Tenenberg, 2007). Conducting the research in Sara's
home helped the investigators gain insights into how she actually addressed real chal-
lenges, as opposed to the more contrived results that might have been seen in the lab.
Four key aspects of this design can be used to describe case studies:

• in-depth investigation of a small number of cases;
• examination in context;
• multiple data sources;
• emphasis on qualitative data and analysis.

7.3.1 IN-DEPTH INVESTIGATION OF A SMALL NUMBER OF CASES
The substantial effort needed to conduct a thorough investigation of each case leads
directly to a practical limit on the number of cases that can be included in any given
study. The entire Shinohara and Tenenberg (Shinohara and Tenenberg, 2007) study
was focused on a single individual: data was collected in her house over the course of
approximately 12 hours, with postmeeting debriefings, transcriptions of audio tapes,
and photos compiled for analysis. The substantial effort required to collect and col-
late this body of data is difficult—if not impossible—to replicate for larger numbers
of participants.
In this regard, case studies are quite different from experiments that ask large
numbers of participants to perform specific, well-defined tasks, leading to results that
can be interpreted as applying to a broad range of users. Case studies use in-depth,
broad examinations of a small number of cases in order to discuss issues that might
provide insights not available in larger user studies. However, this insight comes at a
cost, as the focus on a small number of participants increases the risk that the chosen
cases might be somehow unrepresentative, thus limiting the generalizability of the
conclusions.
Although case studies are small, they need not be limited to only one case.
Involving two or more cases is a highly recommended technique for increasing the