Usability means making products and systems easier to use, and
matching them more closely to user needs and requirements.
The international standard, ISO
9241-11, provides guidance on usability and defines it 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.
Usability is about:
- Effectiveness - can users complete tasks, achieve goals
with the product, i.e. do what they want to do?
- Efficiency - how much effort do users require to do
this? (Often measured in time)
- Satisfaction – what do users think about the
products ease of use?
….which are affected by:
- The users - who is using the product? e.g. are they
highly trained and experienced users, or novices?
- Their goals - what are the users trying to do with
the product - does it support what they want to do with it?
- The usage situation (or 'context of use') - where and
how is the product being used?
Usability should not be confused with 'functionality', however,
as this is purely concerned with the functions and features of the
product and has no bearing on whether users are able to use them
or not. Increased functionality does not mean improved usability!
There are a series of international
standards for usability and user centred design.