HCI: Design for Usability

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HCI Design for Usability

• Based on Chapter 6
• Gregory D. Abowd

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RECALL The Challenges of O-O UI Design

• Two key questions
• How do you create user interface software that
  you can maintain, is well designed,
  object-oriented, is easy to build, and is easy to
  change?
• How do you create user interfaces that people can
  actually use?
• The first was our focus before, and is MUCH
  easier than the second

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What is Human-Computer Interaction?

• The study of people and computing technology and
  the way they influence each other
• H, C I
• 3 Us

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Why study HCI?

• We are surrounded by unusable and ineffective
  systems!
• Its not the users fault!
• Many classes on this (CS 3750)

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Its HARD!

• Design is more difficult when the designer takes
  responsibility.
• Think about the user(s), the situation and make
  the system appropriate.

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Examples of good and bad

Travel is inspirational The microwave in our
apartment in Australia
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Alarm clocks
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There is hopeMy beard trimmer
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But HOW, Gregory?

• Easy to criticize after the fact
• Summative expertise
• Examples abound (bring your own to class on Wed)
• Hard to prevent problems
• Formative expertise
• Ill give you some quick advice

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Don Norman

• http//www.jnd.org/
• Professor of CS and Psych
• Northwestern University
• Nielsen Norman Group
• Formerly
• HP
• Apple
• UCSD
• Writes A LOT!!
• Design of Everyday Things

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Normans formative rules

• Create effective mental models
• Make appropriate functionality visibile
• natural mappings
• Use affordances
• Use constraints
• Provide feedback
• Design with errors in mind

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Natural mappings

• Predictable link between action in the world and
  the consequences
• Related to Normans execution and IF articulation

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Example Toaster Ovens
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Affordances

• Perceived properties
• Relationship between person and object and
  interaction
• Combination of good visibility, natural mapping,
  constraints, feedback

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Constraints

• Convey possible / appropriate actions
• physical (floppy disk, keys)
• semantic (menu graying)
• cultural (red/green)
• logical (spatial)
• Example USB interface

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How to design for usability

• Software Engineering models of design
• Waterfall
• Iterative design / prototyping
• Why is the latter appropriate?

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Evaluation

• Techniques for doing evaluation
• formative vs. summative
• with or without end-users
• using a variety of prototypes
• Specifically,
• Questionnaires, Heuristic evaluation, Cognitive
  walkthrough, think aloud observation

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Questionnaires

• Summative or formative
• Quantitative or qualitative
• Usually inexpensive way to get lots of information

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Questionnaires

• Preparation is expensive, but administration is
  cheap, analysis variable
• Oral (interview) vs. written
• Oral advs Can ask follow-up questions
• Oral disadvs Costly, time-consuming
• Forms can provide better quantitative data

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Questionnaire design

• Take your own survey first
• Know what answers you are trying to elicit and
  dont ask questions you dont need to have
  answered
• Too long, and youll be sorry

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Question Format

• Closed format
• Answer restricted to a set of choices
• Typically very quantifiable
• Variety of styles

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Closed Format

• Likert Scale
• Typical scale uses 5, 7 or 9 choices
• Above that is hard to discern
• Doing an odd number gives the neutral choice in
  the middle

Characters on screen Very hard to read
very easy to read
1 2 3 4 5 6
7
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Other Styles
Rank from 1 - Very helpful 2 - Ambivalent 3 - Not
helpful 0 - Unused
Which word processingsystems do you use?
LaTeX
Word
___ Tutorial ___ On-line help ___ Documentation
FrameMaker
WordPerfect
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Closed Format

• Advantages
• Clarify alternatives
• Easily quantifiable
• Eliminate useless answer

• Disadvantages
• Must cover whole range
• All should be equally likely
• Dont get interesting, different reactions

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Open Format

• Asks for unprompted opinions
• Good for general, subjective information, but
  difficult to analyze rigorously
• May help with design ideas
• Can you suggest improvements to this interface?

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Questionnaire Issues

• Question specificity
• Do you have a computer?
• Language
• Beware terminology, jargon
• Leading questions
• Can be phrased either positive or negative

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Questionnaire Issues

• Prestige bias
• People answer a certain way because they want you
  to think that way about them
• Embarrassing questions
• Hypothetical questions
• Use experience sampling to get reactions in the
  moment

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Heuristic Evaluation

• Have a small set of evaluators independently
  examine an interface and judge its compliance
  with recognized usability principles.
• Mainly formative and qualitative

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Origins of Heuristic Evaluation

• Jakob Nielsen
• Also see Web
• www.useit.com/heuristic
• 1994 case study showed savings of 48 times cost
  of H.E.

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Procedure

• 1. Gather inputs
• 2. Independent evaluation
• 3. Debriefing/Collection
• 4. Severity rating

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Inputs

• Evaluation team (train on method)
• Familiarize with domain
• Storyboards/scenarios showing sufficient
  interface details.

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How many evaluators?
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Independent evaluation

• Judge prototype against set of heuristics
• What heuristics?
• Nielsen list, http//www.useit.com/papers/heuristi
  c/heuristic_list.html
• Yesterdays principles
• Specialized heuristics
• Mankoff, Jennifer, Anind K. Dey, Gary Hsieh,
  Julie Kientz, Scott Lederer, Morgan Ames, (2003).
  "Heuristic Evaluation of Ambient Displays." In
  Proceedings of CHI 2003. 8 pages.

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What is a usability bug?

• Whatever you think is!
• Dont fret worthiness or origin of problem at
  this point.

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Debriefing and Collection

• Organize all found problems
• Discussions now can filter out important problems.

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Severity rating

• Based on
• frequency
• impact
• persistence
• market impact
• 0 to 4 severity scale
• Then pass along recommendations for revisions

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Cognitive Walkthrough

• Evaluates a design for ease of learning
• especially via exploration
• Requires fairly detailed description of prototype
• Analogy to code walkthrough

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CW Procedure

• Define inputs
• Walk through action sequences for task
• Record critical information
• believability story

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Inputs

• Define interaction tasks
• Identify users
• what knowledge experience
• Prototype
• Decompose tasks into action sequences
• must know how interface looks for each step

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Doing the walkthrough

• Address each step of task sequence in turn
• Formulate a believability story
• answer 4 questions

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Question 1

• Will the user be trying to produce whatever
  effect the action has?
• Principle of Rationality applies here
• There is a reason why people do things
• Will user intent match intent for action?

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Common supporting evidence

• It is part of their original task.
• They have experience using the system.
• The system tells them to do it.

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No supporting evidence?

• Construct a failure story.

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Question 2

• Will the user be able to notice that the correct
  action is available?

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Common supporting evidence

• Known through experience
• Visible device, such as a button
• Visible representation of an action, such as a
  menu entry

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Question 3

• Once the user finds the correct action at the
  interface, will she know that it is the right one
  for the effect she is trying to produce?

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Common supporting evidence

• Experience
• The interface provides a prompt or label that
  connects the action to what she is trying to do.
• All other actions look wrong .

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Question 4

• After the action is taken, will the user
  understand the feedback given?

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Common supporting evidence

• Experience
• Recognizing a connection between a system
  response and what she was trying to do.

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Observing Users

• Not as easy as you think
• One of the best ways to gather feedback about
  your interface
• Watch, listen and learn as a person interacts
  with your system

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Observation

• Direct
• In same room
• Can be intrusive
• Users aware of your presence
• Only see it one time
• May use 1-way mirror to reduce intrusiveness

• Indirect
• Video recording
• Reduces intrusiveness, but doesnt eliminate it
• Cameras focused on screen, face keyboard
• Gives archival record, but can spend a lot of
  time reviewing it

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Location

• Observations may be
• In lab - Maybe a specially built usability lab
• Easier to control
• Can have user complete set of tasks
• In field
• Watch their everyday actions
• More realistic
• Harder to control other factors

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Understanding what you see

• In simple observation, you observe actions but
  dont know whats going on in their head
• Often utilize some form of verbal protocol where
  users describe their thoughts

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Engaging Users in Evaluation

• Qualitative techniques
• Think-aloud - can be very helpful
• Post-hoc verbal protocol - review video
• Critical incident logging - positive negative
• Structured interviews - good questions
• What did you like best/least?
• How would you change..?
• Identifying errors can be difficult

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Verbal Protocol

• One technique Think aloud
• User describes verbally what s/he is thinking and
  doing
• What they believe is happening
• Why they take an action
• What they are trying to do
• Example setting the alarm clock

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Think Aloud

• Very widely used, useful technique
• Allows you to understand users thought processes
  better
• Potential problems
• Can be awkward for participant
• Thinking aloud can modify way user performs task

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Cooperative approach

• Another technique Co-discovery learning
  (Constructive interation)
• Join pairs of participants to work together
• Use think aloud
• Perhaps have one person be semi-expert (coach)
  and one be novice
• More natural (like conversation) so removes some
  awkwardness of individual think aloud
• Variant let coach be from design team
  (cooperative evaluation)

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Inputs / Outcomes

• Need operational prototype
• could use Wizard of Oz simulation
• What you get out
• process or how-to information
• compare users (verbalized) mental model to
  designers intended model

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Historical Record

• In observing users, how do you capture events in
  the session for later analysis?

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Capturing a Session

• 1. Paper pencil
• Can be slow
• May miss things
• Is definitely cheap and easy

Task 1 Task 2 Task 3
Time 1000 1003 1008
1022
S e
S e
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Capturing a Session

• 2. Recording (audio and/or video)
• Good for talk-aloud
• Hard to tie to interface
• Multiple cameras probably needed
• Good, rich record of session
• Can be intrusive
• Can be painful to transcribe and analyze

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Capturing a Session

• 3. Software logging
• Modify software to log user actions
• Can give time-stamped key press or mouse event
• Two problems
• Too low-level, want higher level events
• Massive amount of data, need analysis tools

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Alternative

• What if thinking aloud during session will be too
  disruptive?
• Can use post-event protocol
• User performs session, then watches video
  afterwards and describes what s/he was thinking
• Sometimes difficult to recall
• Opens up door of interpretation

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Issues

• What if user gets stuck on a task?
• You can ask
• What are you trying to do..?
• What made you think..?
• How would you like to perform..?
• What would make this easier to accomplish..?
• Maybe offer hints
• This is why cooperative approaches are used
• Can provide design ideas