CS160 Discussion Section 7
Midterm review
David Sun
March 13, 2007
Assignment Concerns
Contextual Inquiry
• Explain the model of interaction
between designer and user in
contextual inquiry and contrast it with
interviewing
Contextual Inquiry
• In contextual inquiry, the designer and user
behave in a master-apprentice fashion, such
that the designer learns about the user’s
tasks in order to understand them. The user
explains how he carries out his work as he
performs them, in front of the designer, at
the user’s workplace.
• On the other hand, an interview becomes a
question-and-answer process such that the
user ceases to perform and explain his
ongoing work.
(continued)
• (You should be able to describe the four
principles of contextual inquiry, how the
master-apprentice model differs from the
interviewer-interviewee, expert-novice, and
host-guest models, the importance of task
analysis, as well as a solid understanding of
how contextual inquiry relates to task
analysis and iterative design.)
Beyer & Holtzblatt reading:
http://inst.eecs.berkeley.edu/~cs160/sp07/readings/f3_beyer_holtzblatt.pdf
Human Centered Design
• In Human-Centered Design, at
what stages of the design process
should the customer or
representative users be involved?
Human Centered Design
• Task analysis, usability testing using
prototypes, and tracking use.
• (This question is vague. Each designer has a
different conceptualization of the exact
stages in the task-centered design process,
and the boundaries between stages are
somewhat blur.)
• (Know not only the stages in which users are
involved, but also how they are involved at
each stage).
Human Model Processor
• Briefly explain what each of the 5 main
parts of the human model processor
does.
Human Model Processor
• Three interacting subsystems
– Perceptual, motor, cognitive
– Serial in action, parallel in recognition.
• Memory stores:
– Working memory: visual image and auditory
image store; finite storage, fast decay time,
physical encoding.
– Long-term memory: infinite storage, no decay,
semantic encoding, knowledge is stored by
associations.
– Working memory = activated portions of longterm memory.
Recognition vs. Recall
• Why is recognition preferred over
recall?
Recognition vs. Recall
• Recall requires the user to reproduce
information from long term memory
– the ease of which differs from user to user
depending on how the information was
originally encoded and stored.
• Recognition presentation of info provides
knowledge that info has been seen before
– easier because of cues to retrieval
Structural vs. Functional
Models
• Contrast structural and functional
models.
Structural vs. Functional
Models
• A structural model explains what the system
does independent of use (it’s a system
centered model)
• functional model explains what the system
does to assist a user’s task (it’s a usercentered model).
Metaphors
• List two (good) user interface metaphors
Metaphors
• Desktop metaphor:
–
–
–
–
–
–
Directories are like folders
Files are like sheets of paper
Windows are like ?:
Menus are like menus
Deleting is like putting in the trash
Running an application program is like
opening the doc.
– Copy to buffer and restore is like cut-andpaste
Metaphors
• Other plausible questions:
– Describe some of the difficulties/issues
associated with the use of metaphors in
interface design.
– Give examples of some bad interface
metaphors…
Conceptual Models
• Other than from a metaphor, where
else do conceptual models come from?
Conceptual Models
• Other existing systems, and social-cultural
norms.
• (Make sure that you also understand how
conceptual models are an improvement over
metaphors, and the significance of
composite metaphors.)
Lo-fi Prototyping
• Give two advantages of rapid prototyping.
Lo-fi Prototyping
• Less time spent in coding.
• Forces designers and users to focus on the big
picture: design of metaphors and mental models
to facilitate uncovering major usability problems
at early stages of interface design.
• (There are several other advantages of rapid
prototyping and you should be aware of them.
You should also understand the relative strengths
and weaknesses between lo-fi and hi-fi
prototyping)
Rettig: “Prototyping for Tiny Fingers”
http://inst.eecs.berkeley.edu/~cs160/sp07/readings/f17_rettig_prototyping.pdf
Heuristic Evaluation Process
• What are some of the advantages of
heuristic evaluation?
• How many testers is a reasonable
number in a heuristic evaluation? Why?
Heuristic Evaluation
• Advantages:
– Cheap
• no special labs or equipment needed
• the more careful you are, the better it gets
– Fast
• on order of 1 day to apply
• standard usability testing may take a week
– Easy to use
• can be taught in 2-4 hours
• Small set (3-5) of evaluators examine UI
– independently check for compliance with usability principles
(“heuristics”)
– different evaluators will find different problems
– evaluators only communicate afterwards
• findings are then aggregated
• Can perform on working UI or on sketches
Heuristic Evaluation Process
• Describe how to perform a heuristic
evaluation.
How to Perform Evaluation
• At least two passes for each evaluator
– first to get feel for flow and scope of system
– second to focus on specific elements
• If system is walk-up-and-use or evaluators
are domain experts, no assistance needed
– otherwise might supply evaluators with scenarios
• Each evaluator produces list of problems
– explain why with reference to heuristic or other
information
– be specific and list each problem separately
Results of Using HE (cont.)
• Single evaluator achieves poor results
– only finds 35% of usability problems
– 5 evaluators find ~ 75% of usability
problems
– why not more evaluators???? 10? 20?
• adding evaluators costs more
• many evaluators won’t find many more
problems
More Questions
• Explain briefly why personas are useful
for design.
• Why is user-interface design based on
iterative refinement, rather than
detailed specification?
(continued)
• How should budget usability methods
be combined with user studies?
• Give some advantages of the masterapprentice model for contextual
inquiry over other kinds of user
questioning.
(continued)
• Which of the following statements best
describes contextual inquiry? Circle all
that apply.
– a) A way of mastering how to perform the
users’ tasks
– b) A way of uncovering usability problems
in a prototype
– c) A way of understanding the users’ needs
and work practices
More tips
• Make sure that you are aware of the major
developments in the history of HumanComputer Interaction, and the pioneers who
were responsible for these advances.
• Know what are the main stages of the human
centered design cycle.
• Be sure that you understand Nelson’s
heuristics and practice applying them in
analyzing an interface design (you should get
plenty from your assignment)
Administrivia
• Wed 3/21 Midterm
• Tue 2/20 Section:
– Run as last-minute Q&A session.
– Bring your questions.