Definition of Usability
April 1, 2013
ISO defines usability as "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)
- effectiveness :
the accuracy and completeness with which specified users can achieve specified goals in particular environments.
- efficiency :
the resources expended in relation to the accuracy and completeness of goals achieved.
- satisfaction :
the comfort and acceptability of the work system to its users and other people affected by its use.
According to Jakob Nielsen, usability is a quality attribute that assesses how easy user interfaces are to use. He saids the word "usability" also refers to methods for improving ease-of-use during the design process. He definded usability 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?
- Satisfaction :
How pleasant is it to use the design?