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 Standards, principles, guidelines

Design experience

Task analysis Design tools

*(incl. usability testing)

Design

Evaluation*

ImplementationFormal models

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

PeterViccellio

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