Web Usability

Usability is all about how quickly and easily users can learn and use a product to successfully achieve its intended goal or purpose. Usability attributes can apply to physical objects, websites, software, and even processes or services.  Most of us never consider usability until we encounter a product with poor usability.

What is Usability?

Usability can be explained in many ways.  These are a few of the most concise and relevant definitions:

[Usability refers to] the extent to which a product can be used by specified users to achieve specified goals with effectiveness, efficiency and satisfaction in a specified context of use.
~ISO 9241-11

Usability is a quality attribute that assesses how easy user interfaces are to use.
~ Jakob Nielsen

After all, usability really just means that making sure that something works well: that a person of average (or even below average) ability and experience can use the thing – whether it’s a Web site, a fighter jet, or a revolving door – for its intended purpose without getting hopelessly frustrated.
~Steve Krug

The study of usability can be considered both a science and an art.  It’s scientific because it can be measured through observation and experimentation.  It can be considered an art because of the roles aesthetics and human perception play.

Core Components of Usability

Learnability is the extent to which users are able to accomplish their intended tasks easily and upon their first exposure to a design.

Efficiency measures the speed at which users can successfully accomplish given tasks once they have become familiar with a design.

Memorability addresses how quickly one can reestablish proficiency with a design after period of not using it.

Errors as an attribute of usability, considers three distinct dimensions: the number of errors encountered, the severity of the those errors, and most importantly, how easily it is for users to recover from the errors.

Satisfaction measures how pleasant a user finds a design.  Although subjective, user satisfaction is a measurable and critical factor of usability.

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