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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.

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Presentation Transcript
  • 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
  • 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?
  • Usability = ???
  • Metrics: What is measurable about usability?
  • How do we know if system A is ‘better than’ system B?
usability metrics
Usability Metrics
  • Ease of learning
  • Ease of use
  • User satisfaction

“user friendly”

usability tradeoffs
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 designrationale

Stories about people and their needs and activities

A problem scenario describes a current situation:

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.

A design scenario describes an initial vision:

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.

What makes a good scenario?

scenario elements
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
*Claims Analysis (see pgs 73-74)
  • Identify an important design feature (cause)
  • Identify the advantages and disadvantages of that feature (effects)

How do you know?

  • Maximize the +’s
  • Minimize the –’s
iterative design
Iterative Design
  • Sometimes design is refinement
iterative design15
Iterative Design
  • Sometimes design is radically transformational

analysis of


field studies

claims about current


Problem scenarios







HCI theory,



analysis of


claims and


Information scenarios

Interaction scenarios






Usability specifications

the changing face of computer use
The Changing Face of Computer Use

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 hci19
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 hci20
Some History of HCI
  • Douglas Engelbart, 1962 “Augmenting Human Intellect: A Conceptual Framework”
  • In 1968, workstation with a mouse, links across documents, chorded keyboard
some history of hci21
XEROX (PARC) Alto and Star








Apple LISA and Mac


High-quality graphics

3rd party applications

Some History of HCI
future of hci
Large displays

Small displays

Peripheral displays

Alternative I/O

Ubiquitous computing

Virtual environments

Augmented Reality

Speech recognition


Media space

Artificial intelligence

Software agents



Future of HCI
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

Center for HCI @ VT
  • VT UGrad Research in CS
  • Andrew Sabri:
      • High-Res Gaming: WarCraft
      • Conference presentation, journal paper
      • Now at Electronic Arts
presentations hall of fame shame
Presentations(Hall of Fame/Shame)
  • See course calendar on website
  • Individual
  • 5% of grade
  • 5 minutes, 3-4 slides
      • Practice
      • Bring on CD, usb key, or laptop
  • Pick UI of your choice (software or real-world)
  • UI critique
      • Scenarios/tasks
      • Claims analysis (include pictures)
      • Redesign ideas?
  • Vote: UI Hall of Fame/Shame
fast food drive thru menus
Fast Food Drive-Thru Menus
  • Scenarios:
      • College students
      • Hungry
      • Get food, get out. FAST!
      • Often: sandwich, fries, drink
      • Typically: Not sure what I want
      • Sometimes: Know what I want
      • Passengers want food too
      • Budget is important
claims 1
Claims 1
  • Billboard menu:
      • + all in one view enables fast recognition & decisions
      • + organized by categories for quick learn
      • + tabular layout, fast for visual scan of prices
      • - see menu too late
      • - passengers can’t see menu
claims 2
Claims 2
  • Microphone/Speaker Voice UI
      • + easy access
      • + human in the loop, error recovery
      • - passengers must order thru driver: slow, errors
      • - winter, Brrrrr!
      • - poor feedback: I can’t understand a word they say
      • - they can’t hear me over my ’87 VW
other good design features
Other good design features
  • Combo meals (high frequency task = fast)
  • Budget menu (Wendy’s)
  • Get price before proceeding
  • Some: visual feedback on order
  • Small re-design ideas:
      • More menus back in line
      • Menu on both sides of car
      • Microphone on both sides
  • Radical: cell phone, in-car UI
homework 1
Homework #1
  • Qualitative discussion
      • Usability problems, errors, access, alternate tasks, …
  • Quantitative discussion
      • Data averages, min, max
      • Data visualization
      • Statistics, t-tests, …