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7.5 Types of case study 165

it for communicating with family and the Internet, forms an important part
of the description. Details of his use of the various components, along with
initial difficulties and their resolutions, are also described (Steriadis and
Constantinou, 2003).
This individual's success may not be generalizable: the system might not
work so well for others. However, this is not the only evaluation found in the
paper. An empirical study of how the typing rates of two additional quadriplegic
users varied with word-prediction schemes formed the basis for a discussion of
factors that might influence typing rate. Even though this study only involved
two users, it provides some insight into the factors that influence success in
using the tool to type text. The case study and the empirical study work together
in a complementary fashion to demonstrate the strengths and limitations of the
proposed system.

The four classes of case study are not mutually exclusive. Sara's case study
has elements of both exploration and explanation. The Interfaces for People with
Alzheimer's Disease sidebar describes a study involving elements of exploration,
description, and demonstration.

7.5 TYPES OF CASE STUDY
7.5.1 INTRINSIC OR INSTRUMENTAL
Case studies are often conducted to shed light on a specific situation. You may be
working with a client to design a new organizational website. A case study of the
client's work processes, corporate organization, and information-sharing practices
and procedures would inform your design process, but the results would be likely to
apply only to that client. These intrinsic studies (Stake, 1995) describe cases that are
of interest to a particular situation.
Case studies can also work towards developing a broader understanding. These
instrumental case studies ask questions in the hope of generating insights that go
beyond the case at hand. They become tools that lead to a broader understand-
ing. Sara's case study involved the instrumental goal of identifying difficulties and
workarounds that might be used by many others—not just Sara (Shinohara and
Tenenberg, 2007).
Case studies can be both intrinsic and instrumental: it might be argued that Sara's
case is both interesting in its own right (intrinsic) and aimed at broader understanding
(instrumental).

7.5.2 SINGLE CASE OR MULTIPLE CASES
Although Sara's case study focused on one person's use of technology, case studies
are certainly not limited to single cases. The use of multiple cases may initially seem