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7.3 What is a case study? 157

credibility of both analyses and results (Yin, 2014). As we will see, the precise defini-
tion of a case is not clear (Section 7.5.2). Was Sara's study an example of a case study
with one case—the individual—or with twelve cases—the tasks? Answers to these
questions are not necessarily obvious.
Case studies are closely related to ethnographic research (Chapter 9) in that both
approaches involve close, qualitative examination of a small number—often only
one—of situations. Although case studies often use ethnographic observation tech-
niques, classic ethnographic studies are usually more in-depth, conducted over lon-
ger periods of time, and more likely to involve a mix of participation and observation
than case studies. As the line between case studies and ethnography is often some-
what blurred, it is often best to focus on the techniques used for data collection and
analysis, rather than on the label applied to the study.

7.3.2 EXAMINATION IN CONTEXT
Lab-based usability studies have a huge role to play in HCI research. The controlled
environments of usability labs are wonderful for removing undesired external influ-
ences, but they do not provide a very realistic picture of how people really work.
Computer use generally takes place at homes or offices that have distractions, com-
peting concerns demanding attention, and the stress of multitasking in the hopes of
meeting competing deadlines. As these factors do not arise in controlled usability
labs, observations made in the lab might not generalize to “real-world” behavior.
Unlike lab-based experiments, case studies focus on observation of phenomena
in a meaningful context that is beyond the control of the investigator. By observing
and closely watching activities as they occur in the real world, free from the prede-
termined goals and narrowly defined questions that often accompany usability stud-
ies and controlled experiments, researchers can use case studies to develop detailed
understandings of interaction techniques and coping strategies—understandings that
might be hard (if not impossible) to develop through usability studies. In this sense,
case studies can be very similar to ethnographic research (Chapter 9), although case
studies generally (although not always) lack the participatory aspect associated with
some ethnographic studies. Further comparison between case studies and ethnogra-
phies can be found in Chapter 9.

7.3.3 MULTIPLE DATA SOURCES
Case studies often rely upon multiple data collection techniques to act as sources of
corroborating evidence. In Shinohara and Tenenberg (Shinohara and Tenenberg, 2007),
three types of technology biographies (Blythe et al., 2002) were used: demonstrations
of devices (technology tours), reflections on memories of early use of and reactions to
devices (personal histories), and wishful thinking about possible technological innova-
tions (guided speculation). More generally, these data sources are examples of three
commonly used types of case study data: artifacts, observation, and interviews. The case
study of Sara also involved the impressions and subjective responses of the researchers.