Transcript User-Centered System Design

User-Centered System Design
User-Centered System Design
- a philosophy of user interface design
introduced by Don Norman & Steve
Draper in 1986
User-Centered System Design
Technology should be designed around
the needs of the user.
To do this, you need to understand users
and what they are trying to do.
Avoid: Solutions in search of a problem!
User-Centered System Design
Requirements analysis
Task analysis
Standards, principles, guidelines
Design experience
Design tools
Design
Formal models
Implementation
Evaluation*
*(incl. usability testing)
User-Centered System Design
To what extent can you trust your own
intuitions about doing a task?
You can’t!!!
(Norman)
The interface should be the
responsibility of someone who can
take the perspective of the user and
be a strong advocate.
This is not easy!
User-Centered System Design
Some principles
 focus on users and their needs instead
of technical considerations
 do a task analysis
 start usability testing & evaluation early
in the design process
 design the system iteratively
and allow it to evolve
Iterative Design
DESIGN
TEST
Task analysis
Task analysis - What is it?
observes users in realistic settings
doing particular tasks
 a bit like doing anthropology or
ethnography
 may include taking notes on what users
actually do, having them “think out loud”
while working, interviewing them, or
having them fill out questionnaires

Task analysis
can be done at different levels of detail
 fine level (primitives, e.g. therbligs,
keystrokes,GOMS - the “micro” level)
 intermediate level (flow charts, plans,
or steps for sequences of actions)
 high level (cognitive goals; social
impact - the “macro” level)
The goals of task analysis
enables you to understand what the
user has to do and cope with
 enables you to trace steps leading up to
an error and figure out why it occurred
 enables you to see what parts of the
task the user spends the most time
doing - what is easy and what is hard
 enables you to compare different users
and different methods for doing tasks

Methods for task analysis
 Questionnaires
 Interviews
 Ethnographic
observation
 Verbal protocols
 Formal models and simulations
Questionnaires & interviews
 are
often done badly.
 It’s important to ask open-ended
questions first and to avoid biasing the
respondent (avoid leading questions).
 Respondents often misinterpret
questions.
 Problem: trusting what people say
Ethnographic observation
a
method from anthropology
 Example: Lucy Suchman’s studies of
people using copy machines (at Xerox)
Finding:
Human action isn’t all planned ahead people respond to the situation they are
in (“situated action”)
Ethnographic observations
are very different
from observations in the laboratory!
(We’ll compare these further in our next lecture)
A note on scientific methods:
There are two important steps in doing
science:
1. Observing and describing
2. Testing theories and hypotheses
HCI specialists get many useful principles and
solutions from what they see users do, not
only from abstract theory and testing
hypotheses.
Methods for task analysis (cont.)
 Questionnaires
 Interviews
 Ethnographic
observation
 Verbal protocols
 Formal models and notations
(GOMS)
(Hierarchical task analysis)
Verbal protocols
 pioneered
by psychologists studying
problem-solving
 have people “think out loud” as they do
some activity, step by step
 Advantage: can get at some of the
invisible steps that people go through
on the way to a solution, steps that
aren’t evident in their behavior.
Challenges in task analysis:
You must involve other people!
 Try to avoid bias.
 Summarize in some useful form.
 Try to characterize the full range of
relevant tasks and users.

When to do task analysis?
Task analysis must be done at the very
beginning of the design process.
Examples:
 Back Seat Driver
 NL interface (HP)
 Communication device for a severely
handicapped user
How to summarize data from
task analyses?
Scenarios - imaginary but
representative, at a useful level of detail
 Describe different types of users, tasks
 Characterize their different perspectives
 Quantify (to the extent possible) their
tasks and problem areas

IDEO web site:
An interesting company that specializes in
task analysis, design, and usability
Peter
Viccellio
Quic kT ime™ and a
T IFF (Uncompres sed) decompres sor
are needed to s ee this picture.