Transcript CS3205, HCI in Software Development Usability Goals, Principles, Guidelines

CS3205, HCI in Software
Development
Usability Goals, Principles,
Guidelines
(Introduction, Part 2)
Spring 2013
Reminder….
• users should be involved through the
development of the project
• specific usability and user experience goals
need to be identified, clearly documented and
agreed at the beginning of the project
• iteration is needed through the core activities
Towards More Usable Systems
• Seems like we need the following:
– Goals we want to achieve
– Principles on how to achieve these
– Lists of do’s and don’ts
– Theories that underlie principles, lists
– Methods for measuring and evaluating
Usability Goals
• Here’s one set (from the ID textbook)
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Effective to use
Efficient to use
Safe to use
Have good utility
Easy to learn
Easy to remember how to use
Usability Goals
• Effective to use (effectiveness)
– A general goal: how well does a system do what it
should do?
• Efficient to use (efficiency)
– Do things quickly, easily.
– Especially common tasks.
• Safe to use (safety)
– Protect people from hazards (usually not a SW issue)
– Help prevent user from making errors and recover
from errors
– Give users confidence
Usability Goals (2)
• Have good utility
– Has the right kind of functionality
– Supports users in accomplishing tasks
• Easy to learn (learnability)
– Includes how easy it is to learn advanced
features. (If hard, who bothers?)
• Easy to remember how to use
(memorability)
– Many systems used infrequently
How to Measure Usability?
• We want to achieve these goals, but how
do we know?
• Develop measurable criteria based on
previous goals. Examples:
– Time to learn
– Speed of performance
– Rate of errors over by users
– Retention over time
– Subjective satisfaction
User experience (UX) goals
– Satisfying
- rewarding
– Fun
- support creativity
– Enjoyable
- emotionally fulfilling
– Entertaining
…and more
– Helpful
– Motivating
– Aesthetically pleasing
Usability and user experience
goals
• How do usability goals differ from user
experience goals?
– How easy is it to measure usability versus
user experience goals?
• Are there trade-offs between the two kinds
of goals?
– e.g. can a product be both fun and safe?
In-class Exercise
• Consider the SW listed on the board
– Which usability goals and user experience
goals are important and not important?
– Identify some strengths and weaknesses for
usability and user experience goals for the
SW.
• Break into groups of 4 and discuss, make
notes, and be ready to report to the class
(after 10 minutes discussion).
Facebook
• What matters?
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Efficiency – use often and quickly
Learnability – new people can get hooked quickly
Many user experience goals matter
Safety – oversharing, up to user
• What’s good/bad?
– Effic. – type name, search bar, importnt links top-left,
people you care about
– Learnability/memorability – stop changing things!
Never change everything at once.
Collab
• What matters or not?
– Utility – needs to have tools for all things with class
– Learnability
– Safety: tests, quizzes, submissions – mistake has a
big impact
• What’s good or bad?
– Testing tool: use arrows to move page vs. answer
– Consistency in tool choice: impacts learnabilty,
memorability
– Submit, forget to click pledge, lose work!
Android
• Efficiency matters
– Depends on user – customize home page,
easy to move between page
• Connect to pc, synching
– More user control for synch than with iOS
• Typing issue
Reminder of where we are
1. Usability Goals
•
Some measures
2. User Experience Goals
3. Design Principles
– First two were higher level (goals)
– Now talking about guidance for how to
achieve goals
4. Guidelines (guidance as lists)
Design principles
• Generalizable abstractions for thinking about
different aspects of design
• The do’s and don’ts of interaction design
– But at a high level. (Compare to guidelines later.)
• What to provide and what not to provide at
the interface
• Derived from a mix of theory-based
knowledge, experience and common-sense
Higher-level Principles
• Now, we’ll talk about the following:
– Visibility
– Feedback
– Constraints
– Mapping
– Consistency
– Affordances
• Ideas well-known (e.g. from Norman’s
Design of Everyday Things)
Activity (Mini-Homework)
• Do this on your own on in pairs
• Go find two examples of problems in the GUIs of
software apps or the UI of a interactive device
(not Web pages)
– Problem must illustrate a violation of one of the
following design principles (not the previous usability
goals)
– Describe the problems in these terms
• Write on a single-page for class display next
class!
Visibility
• This is a control panel for an
elevator.
• How does it work?
• Push a button for the floor you want?
• Nothing happens. Push any other
button? Still nothing. What do you
need to do?
It is not visible as to what to do!
From:
www.baddesigns.com
Visibility
…you need to insert your room
card in the slot by the buttons to
get the elevator to work!
How would you make this action more visible?
• make the card reader more obvious
• provide an auditory message, that says what to
do (which language?)
• provide a big label next to the card reader that
flashes when someone enters
• make relevant parts visible
• make what has to be done obvious
Feedback
• Sending information back to the user about
what has been done
• Includes sound, highlighting, animation and
combinations of these
– e.g. when screen button clicked on provides
sound or red highlight feedback:
“ccclichhk”
Constraints
• Restricting the possible actions that can be
performed
• Helps prevent user from selecting incorrect
options
• Three main types (Norman, 1999)
– physical
– cultural
– logical
Physical constraints
• Refer to the way physical objects restrict the
movement of things
– E.g. only one way you can insert a key into a lock
• How many ways can you insert a CD or DVD
disk into a computer?
• How physically constraining is this action?
• How does it differ from the insertion of a floppy
disk into a computer?
Logical constraints
• Exploits people’s everyday common sense
reasoning about the way the world works
• An example is the logical relationship between
physical layout of a device and the way it works
– See next slide for an illustration
Logical or ambiguous design?
• Where do you plug the
mouse?
• Where do you plug the
keyboard?
• top or bottom
connector?
From: www.baddesigns.com
• Do the color coded
icons help?
More Logically Constrained
Provides direct adjacent
mapping between
icon and connector
Provides color coding to
associate the
connectors with the
labels
From: www.baddesigns.com
Cultural constraints
• Learned arbitrary conventions
like red triangles for warning
• Can be universal or culturally specific
– For SW we’ve accepted certain conventions,
e.g. we know what to do with an icon
• Be concerned of cross-cultural conventions
and other ambiguities!
– Does an “X” mean “selected” or “not selected”
– Is a check-mark better?
Which are universal and which
are culturally-specific?
Mapping
• Relationship between controls and their
movements and the results in the world
• Why is this a poor mapping of control
buttons?
Mapping
• Why is this a better mapping?
• The control buttons are mapped better onto the
sequence of actions of fast rewind, rewind, play
and fast forward
– Is this a logical mapping (in most people’s minds)?
– Is there a mapping that makes more sense?
Mappings in the Kitchen
– Which controls go with which rings
(burners)?
A
B
C
D
Why is this a better design?
Example:
• What’s wrong?
What principle?
• Pantech Breeze 3
– Softkeys: “Options”,
“Select”, and “Back”
Consistency
• Design interfaces to have similar operations and
use similar elements for similar tasks
• For example:
– always use ctrl key plus first initial of the command for
an operation – ctrl+C, ctrl+S, ctrl+O
• Main benefit is consistent interfaces are easier
to learn and use
• But… didn’t a wise man say this?
Consistency is the hobgoblin of little minds.
– A foolish consistency is the hobgoblin of little minds
(adored by little statesmen and philosophers and
divines)
When consistency breaks down
• What happens if there is more than one
command starting with the same letter?
– e.g. save, spelling, select, style
• Have to find other initials or combinations of
keys, thereby breaking the consistency rule
– E.g. ctrl+S, ctrl+Sp, ctrl+shift+L
• Is this desirable? Does it defeat the purpose?
– It may increase learning burden on user
– It may make them more prone to errors
– But it may still benefit frequent or experienced users
Internal and external
consistency
• Internal consistency refers to designing
operations to behave the same within an
application
– Difficult to achieve with complex interfaces
• External consistency refers to designing
operations, interfaces, etc., to be the same
across applications and devices
– Very rarely the case, based on different designer’s
preference
– Most successful in product families (e.g MS Office)
– Op. Sys. vendors may define style guidelines
Keypad numbers layout
• A case of external inconsistency
http://www.howstuffworks.com/question641.htm
(a) phones, remote controls
(b) calculators, computer keypads
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0
Affordances: to give a clue
• Refers to an attribute of an object that allows
people to know how to use it
– E.g. a mouse button invites pushing, a door handle
affords pulling
• Norman (1988) used the term to discuss the
design of everyday objects
• Since then has been popularized in interaction
design to discuss how to design interface
objects
– E.g. scrollbars to afford moving up and down, icons to
afford clicking on
What does ‘affordance’ have to
offer interaction design?
• Notion of affordance is often over-used!
http://www.jnd.org/dn.mss/affordances-and.html
• Interfaces are virtual and do not have
affordances like physical objects
• Norman argues it does not make sense to talk
about interfaces in terms of ‘real’ affordances
• Instead interfaces are better conceptualised as
‘perceived’ affordances
– Learned conventions of arbitrary mappings between
action and effect at the interface
– Some mappings are better than others
Activity 1.3
– Physical affordances:
How do the following physical objects afford? Are
they obvious?
Activity 1.4
– Virtual affordances
How do the following screen objects afford?
What if you were a novice user?
Would you know what to do with them?
Activity 1.5: Physical and Perceived
Affordances
• Take a cell phone, digital camera, or PDA
– Have laptop? Open a fancy SW app: Outlook,
Eclipse, etc?
• In a small group
– Identify any physical affordances the device has
– Identify any perceived or visual affordances the
software user interface has
• Write these down, be prepared to share or turn
in
A Good Example
• Kodak DC-290 digital camera
Adjusting Tabs in MS Word
• What’s the idea here? Problems?
• What principle(s)?
– Affordance
– Metaphor (more on this later)
Affordance Examples
• Your ideas here!
Web Links
• What are the conventions that help you
recognize a link?
• Would you are argue this is an affordance?
– A perceived affordance – convention of a mapping
between action and effect
– Does it “afford” clicking on it?
• Examples of problems with this?
– Websites that change CSS for links. Examples?
Activity (Mini-Homework)
• Do this on your own on in pairs
• Go find two examples of problems in the GUIs of
software apps or the UI of a interactive device
(not Web pages)
– Problem must illustrate a violation of one of the
previous design principles (not the earlier usability
guidelines)
– Describe the problems in these terms
• Write on a single-page for class display next
class!
Example:
• What’s wrong?
What principle?
• Collab’s site
selector
• Shows all Collab
sites you belong
too
Example:
• What’s wrong? What principle?
• OS X Finder
Example:
• What’s wrong?
What principle?
• SIS result of
student search
Overview (Reminder)
1. Usability Goals
2. User Experience Goals
3. Design Principles
4. Guidelines
– Still talking about guidance for how to
achieve goals
– These are more prescriptive (do’s & don’ts)
Guidelines
• What do we mean by “guidelines”?
– Tell me!
• Are guidelines enough? Lead to
problems?
– Too specific, incomplete. Don’t generalize to
all situations
– But… Capture experience and best practices
• Many examples of guidelines…
Nature of Guidelines
• Similar to design principles, except more
prescriptive
• Used mainly as the basis for evaluating
systems
• Provide a framework for heuristic
evaluation
– We’ll talk about particular approach to
evaluation this later
Jakob Nielsen Says…
• Jakob Nielsen: a leading figure in usability
– Member of the Nielsen Norman Group
• Donald Norman
• Bruce "Tog" Tognazzini
– http://www.useit.com/
– Alertbox: regular “column”
– Wikipedia:
http://en.wikipedia.org/wiki/Jakob_Nielsen_(usability_consultant)
“Usability principles” (Nielsen 2001)
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Visibility of system status
Match between system and the real world
User control and freedom
Consistency and standards
Help users recognize, diagnose and recover
from errors
Error prevention
Recognition rather than recall
Flexibility and efficiency of use
Aesthetic and minimalist design
Help and documentation
Read More about Nielsen’s List(s)
• Nielsen’s site has more on the previous list
http://www.useit.com/papers/heuristic/heuristic_list.html
• Heuristics: more general “guidelines”
– We’ll see this term again
– Heuristic evaluation
• Activity 1.7 for you to do:
– Find one list of similar usability principles (i.e
heuristics, prescriptive guidelines, do’s/don’ts) for
Web page design
– Write it down – we’ll collect these
– Go find one now! We’ll share.
• Are design principles reflected in these?
Shneiderman’s Eight Golden
Rules
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Strive for consistency
Cater to universal usability
Offer informative feedback
Design dialogs to yield closure
Prevent errors
Permit easy reversal of actions
Support internal locus of control
Reduce short-term memory load.
More Specific Guideline Examples
from DTUI
• Shneiderman’s text (DTUI) gives some
more detailed examples
– National Cancer Institute, p. 62
– W3C, Accessibility, p. 62
– Display organization, p. 63
– Control rooms, p. 63
– Others in Section 2.2
• Ask yourself: what principle(s) underlie
each guideline?
Ex. 1: National Cancer Institute
• 388 guidelines for informative web pages,
such as:
– Reduce user’s workload
– Do not display unsolicited windows or graphics
– Standardize task sequences
– Ensure embedded links are descriptive
– Use unique and descriptive headings
– Develop pages that print properly
– Use thumbnail images to preview large images
Ex. 2a, Organizing Data Display
• From Smith and Mozier (1986).
• Data display: 5 high-level goals
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Consistency of data display
Efficient information assimilation by the user
Minimal memory load on the user
Compatibility of data display with data entry
Flexibility for user control of data display
• Data entry: 5 similar high-level goals, but also:
– Minimal input actions by user
Ex. 2b, More Specific than 2a
• Lockheed (1981) on control rooms
– Be consistent in labeling, graphics, formatting
– Standardize abbreviations
– Present data only if it assists the operator
– Present data graphically where appropriate
instead of numbers and text
– Rely on monochromatic displays with good
spacing and arrangement, saving color for
when it helps
– Involve users in development of displays