Usability
Usability is the broad discipline of applying scientific principles to ensure that the system/site designed is easy to learn, easy to use, easy to remember, error tolerant, and subjectively pleasing.
There is a set of international (ISO) standards on usability defining it as:
"the extent to which a product can be used by specified users to achieve specific goals with effectiveness, efficiency, and satisfaction in a specified context of use.
"Shackel's (1986) says for a system to be usable the following must be achieved:
Effectiveness
At better than some required level of performance (e.g. in terms of speed and errors).
By some required percentage of the specified target range of users.
Within some required proportion of the range of usage environments.
Learnability
Within some specified time from installation and start of user training.
Based upon some specified amount of training and user support.
And within some specified amount of training and user support.
Flexibility
With flexibility allowing adaptation to some specified percentage variation in task and/or environments beyond those first specified.
Attitude
And within acceptable levels of human cost in terms of tiredness, discomfort, frustration and personal effort.
So that satisfaction causes continued and enhanced usage of the system.
Glossary
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