What is usability?
Usability testing is a means for measuring how well people can employ a human-made object to achieve a particular goal.
Usability measures the quality of a user’s experience when interacting with a product or system—whether it’s a web site, a software application, mobile technology, or any user-operated device.
In general, usability refers to how well users can learn and use a product to achieve their goals and how satisfied they are with that process. Usability, as defined by Joseph Dumas and Janice (Ginny) Redish, means that people who use the product can do so quickly and easily to accomplish their tasks. Usability may also consider such factors as cost-effectiveness and usefulness.
A key methodology for carrying out usability is called User-Centered Design.
What does usability measure?
It is important to realize that usability is not a single, one-dimensional property of a user interface. Usability is a combination of factors including:
- Ease of learning – How fast can a user who has never seen the user interface before learn it sufficiently well to accomplish basic tasks?
- Efficiency of use – Once an experienced user has learned to use the system, how fast can he or she accomplish tasks?
- Memorability – If a user has used the system before, can he or she remember enough to use it effectively the next time or does the user have to start over again learning everything?
- Error frequency and severity – How often do users make errors while using the system, how serious are these errors, and how do users recover from these errors?
- Subjective satisfaction – How much does the user like using the system?
(adapted from www.usability.gov)
ISO 9241-11 usability framework consists of the users, tasks, equipment (hardware, software and materials), and the physical and organizational environments which may all influence the usability of a product.
Figure: ISO 9241-11 framework