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CHAPTER
7
Case studies

7.1 INTRODUCTION
Research into human-computer interaction (HCI), like most other research, is often
a numbers game: the more, the merrier. Whether you are collecting data to help you
understand the requirements for a new system, evaluating the usability of a new sys-
tem, or conducting an empirical study aimed at validating a new theory, more partici-
pants are better. It takes more time and effort to run 20 subjects than 10 and it may be
harder to find 100 people than 30 for focus groups, but the advantages are significant.
When you involve large numbers of people, you get a broader, more representative
sample. With a small number of people, your chances of getting outliers—those who
are significantly faster or slower, inexperienced or expert—are vastly increased. For
empirical studies, results that may be statistically ambiguous with a small group may
be much clearer with a larger sample.
Unfortunately, for some research projects, a large sample is extremely difficult, if
not completely impossible. Fortunately, this is not a cause for despair. Case studies,
in which researchers study a small number of participants (possibly as few as one)
in depth, can be useful tools for gathering requirements and evaluating interfaces.
A case study is an in-depth study of a specific instance (or a small number of in-
stances) within a specific real-life context. Close examination of individual cases can
be used to build understanding, generate theories and hypotheses, present evidence
for the existence of certain behavior, or to provide insight that would otherwise be
difficult to gather. Case studies often use theoretical frameworks to guide both the
collection of data from multiple sources and the analysis of the data (Yin, 2014).
However, statistical analyses are not the goal. Instead, case studies use careful analy-
sis of carefully selected subjects to generate interesting and novel insights, ideally
with an eye on developing general principles that might facilitate understanding of
other cases.
Case studies present a different set of challenges from studies involving larger
numbers of participants. The first question you might face is determining whether or
not a case study is appropriate. Given the small sample size, identifying appropriate
participants may be even more important than it is for larger studies. The duration,
content, and format of the study will depend upon your goals and resources. Finally,
data analysis and interpretation are particularly important: you may want to be care-
ful about making broad, sweeping claims based on your study of one case.

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