Scenario-Based Usability Engineering

Chris North

CS 3724: HCI

Outline

• Scenario-based usability engineering:• Engineering• Usability

– Metrics– Tradeoffs

• Scenario-based– Scenarios– Claims analysis

• HCI background:• History• @ VT

• Class stuff:• HoF/S presentations• HW 1• Project

Engineering

• What is “engineering”?

• What is “science”?

• Myth: The user interface is tacked on at the end of the project

• Why don’t Waterfall models work?

Palm vs. Newton

Usability

• Usability = ???

• Metrics: What is measurable about usability?

• How do we know if system A is ‘better than’ system B?

Usability Metrics

• Ease of learning• learning time, retention time

• Ease of use• user performance time, error rates

• User satisfaction• surveys

“user friendly”

Usability Tradeoffs

• Can we simultaneously optimize all usability metrics?

• What factors impact tradeoff decisions?

• In usability engineering:• Identify tradeoffs

• Choose based on design goals

• Track tradeoffs for design rationale

Paper Pad vs. MS Word

+

-

+

-

Scenarios

Marissa was not satisfied with her class today on gravitation and planetary motion. She is not certain whether smaller planets always move faster or how a larger or denser sun would alter the possibilities for solar systems.

She stays after class to speak with her teacher, Mr. Boring, but she isn’t able to pose these questions clearly yet, so Mr. Boring suggests that she re-read the text and promises more discussion tomorrow.

Stories about people and their needs and activities

A problem scenario describes a current situation:

Marissa, a 10th-grade physics student, is studying gravity and its role in planetary motion. She goes to the virtual science lab and navigates to the gravity room.

In the gravity room, she discovers two other students, Randy and David, already working with the Alternate Reality Kit, which allows students to alter various physical parameters (such as the universal gravitational constant) and then observe effects in a simulation world.

The three students, each of whom is from a different school in the county, discuss possible experiments by typing messages from their respective personal computers. Together they build and analyze several solar systems, eventually focusing on the question of how comets can disrupt otherwise stable systems.

They capture data from their experiments and display it with several visualization tools, then write a brief report and send it for comments to her teacher Mr. Wright, who uses it for class discussion the next day.

A design scenario describes an initial vision:

What makes a good scenario?

Scenario Elements

• Setting• Actors (people, users)• Task goals (what I want to achieve)• Plans (how I will accomplish it)• Actions (do it)• Events (system response)• Evaluation (is that what I wanted?)

What are the advantages of scenarios?

*Claims Analysis (see pgs 73-74)

Collaboration of multiple students

(high-level design)

+ students can learn from each other

+ encouragement

- competition for control

- distraction

Drag-and-drop planets into solar system

(detailed design)

+ easy to learn for short term usage

+ fun game-like, keeps students interested

- difficult to get precise placement

- difficult for repeatable experiments

1. Identify an important design feature (cause)2. Identify the advantages and disadvantages of that feature (effects)

How do you know?

Design

• Maximize the +’s

• Minimize the –’s

Collaboration of multiple students

+ students can learn from each other

+ encouragement

- competition for control

- distraction

Private simulation space?

?

Iterative Design

• Sometimes design is refinement

Iterative Design

• Sometimes design is radically transformational

Problem scenarios

summativeevaluation

Information scenarios

claims about current practice

analysis ofstakeholders,field studies

Usability specifications

Activityscenarios

Interaction scenarios

iterativeanalysis ofusability claims andre-design

metaphors,informationtechnology,HCI theory,guidelines

formativeevaluation

DESIGN

ANALYZE

PROTOTYPE & EVALUATE

Some History of HCI

The Changing Face of Computer Use

1960’s

1970’s

1980’s

1990’s

2000+

Professional programmers,“software psychology”

Business professionals,mainframes, command-line

Large, diverse user groups,“the computer for the rest of us”

World Wide Web and more,information access & overload

Ubiquitous computing,diversity in task, device, …

Some History of HCI

• Vannevar Bush, 1945 “As We May Think”

• Vision of post-war activities, Memex

• “…when one of these items is in view, the other can be instantly recalled merely by tapping a button”

Some History of HCI

• Douglas Engelbart, 1962 “Augmenting Human Intellect: A Conceptual Framework”

• In 1968, workstation with a mouse, links across documents, chorded keyboard

• XEROX (PARC) Alto and Star– Windows– Menus– Scrollbars– Pointing– Consistency– OOP– Networked

Some History of HCI

• Apple LISA and Mac– Inexpensive

– High-quality graphics

– 3rd party applications

Future of HCI

• Large displays• Small displays• Peripheral displays• Alternative I/O• Ubiquitous computing• Virtual environments• Augmented Reality

• Speech recognition• Multimedia• Media space• Artificial intelligence• Software agents• Games• ...

Center for HCI @ VT

• Doug Bowman• Dan Dunlap• Roger Ehrich• Steve Harrison• Rex Hartson• Deborah Hix• Andrea Kavanaugh• Brian Kleiner• Scott McCrickard• Chris North• Manuel Perez

• Francis Quek• Tonya Smith-Jackson• Deborah Tatar• Woodrow Winchester

VT GigaPixel Display

VTURCS

• VT UGrad Research in CS

• http://vturcs.cs.vt.edu

• Andrew Sabri:• High-Res Gaming:

WarCraft

• Conference presentation, journal paper

• Now at Electronic Arts

Assignment

• Read: UE chapter 2 (Requirements Analysis)

• HoF/S Presentations– Allan tran, josh wu

• Homework #1

• Project Teams

Homework #1

• Qualitative discussion• Usability problems, errors, access, alternate tasks, …

• Quantitative discussion• Data averages, min, max

• Data visualization

• Statistics, t-tests, …

Projects