What
is usability
Any system designed
for people should be easy to use, easy to learn, easy to remember, and helpful
to users.
Usability is defined by 5 quality components:
- Learnability : How easy is it for users to accomplish basic tasks the first time they encounter the design?
- Efficiency: Once users have learned the design, how quickly can they perform tasks?
- Memorability : When users return to the design after a period of not using it, how easily can they reestablish proficiency?
- Errors:
How many errors do users make, how severe are these errors, and how easily
can they recover from the errors?
- Satisfaction:
How pleasant is it to use the design?
Usability testing is done from the users point of view.
This testing type makes an attempt to describe the “look and feel” and usage
features or usage aspects of a product.
Nowadays there are many tools available in the market
to perform the test.
Important
factors while designing a site that focuses on usability
John Gould and
Clayton Lewis recommend that designers striving for usability follow these
three design principles. - Early focus on users and tasks
- Empirical
measurement
- Iterative
design
According to Jakob Nielsen, these are the ten general principles
for user interface design. They are called "heuristics" because they
are more in the nature of rules of thumb than specific usability guidelines.
Visibility of system status
The system should
always keep users informed about what is going on, through appropriate feedback
within reasonable time.
Match between system and the real world
The system should
speak the users' language, with words, phrases and concepts familiar to the
user, rather than system-oriented terms. Follow real-world conventions, making
information appear in a natural and logical order.
User control and freedom
Users often choose
system functions by mistake and will need a clearly marked "emergency
exit" to leave the unwanted state without having to go through an extended
dialogue. Support undo and redo.
Consistency and standards
Users should not
have to wonder whether different words, situations, or actions mean the same
thing. Follow platform conventions.
Error prevention
Even better than
good error messages is a careful design which prevents a problem from occurring
in the first place. Either eliminate error-prone conditions or check for them
and present users with a confirmation option before they commit to the action.
Recognition rather than recall
Minimize the user's
memory load by making objects, actions, and options visible. The user should
not have to remember information from one part of the dialogue to another.
Instructions for use of the system should be visible or easily retrievable
whenever appropriate.
Flexibility and efficiency of use
Accelerators --
unseen by the novice user -- may often speed up the interaction for the expert
user such that the system can cater to both inexperienced and experienced
users. Allow users to tailor frequent actions.
Aesthetic and minimalist design
Dialogues should
not contain information which is irrelevant or rarely needed. Every extra unit
of information in a dialogue competes with the relevant units of information
and diminishes their relative visibility.
Help users recognize, diagnose, and recover from errors
Error messages
should be expressed in plain language (no codes), precisely indicate the
problem, and constructively suggest a solution.
Help and documentation
Even though it is
better if the system can be used without documentation, it may be necessary to
provide help and documentation. Any such information should be easy to search,
focused on the user's task, list cconcrete steps to be carried out, and not be
too large.
Site
with good example of usability design
I found this site which talks about 20 websites to designhttp://sixrevisions.com/usabilityaccessibility/20-websites-to-help-you-master-user-interface-design/
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