Usability and the Web
Background
Usability refers to a quality attribute that assesses how easy user interfaces are to use. The term is also used to refer to a number of techniques and methods for improving usability during the various stages of design and development.
What Does Usability Include?
Usability can be separated into several components [1] such as:
- Learnability:
- How easy it is to get to grips with an unfamiliar interface?
- Efficiency:
- How quickly an experienced user can perform a given task?
- Memorability:
- Once familiar with an interface, is it easily forgettable?
- Errors:
- How easy is it to make mistakes/recover from mistakes?
- Satisfaction:
- Is the design enjoyable to use?
These characteristics are all useful metrics, although the importance of each one depends on the expected uses of the interface in question. In some circumstances, such as software designed for a telephone switchboard operator, the time it takes for a skilled user to complete a task is rather more important than learnability or satisfaction. For an occasional web user, a web site's designers may wish to focus principally on providing a site that is learnable, supports the user, and is enjoyable to use. Designing a usable site therefore requires a designer to learn about the needs of the site's intended users, and to test that their design meets the criteria mentioned above.
Why Does Usability Matter?
More attention is paid to accessibility than to usability in legislation, perhaps because accessibility is perceived as a clearly defined set of guidelines, whilst usability itself is a large and rather nebulous set of ideas and techniques. However, a Web site can easily pass accessibility certification, and yet have low usability; accessibility is to usability what legible handwriting is to authorship. Interfaces with low usability are often frustrating, causing mistakes to be made, time to be wasted, and perhaps impede the user from successfully reaching their intended goal at all. Web sites with low usability will not attract or retain a large audience, since if a site is perceived as too difficult to use, visitors will simply prefer to take their business elsewhere.
Usability Testing
User testing is traditionally an expensive and complicated business. Fortunately, modern discount ('quick and dirty') methods have changed this, so that it is now possible to quickly test the usability of a web site at any stage in its development. This process, of designing with the user in mind at all times, is known as user-centred design. At the earliest stages, an interface may be tested using paper prototypes or simple mockups of the design. It is advisable to test early and often, to ensure that potential problems with a design are caught early enough to solve cheaply and easily. However, completed Web sites also benefit from usability testing, since many such problems are easily solved.
User testing can be as simple as asking a group of users, chosen as representative of the expected user demographic, to perform several representative tasks using the Web site. This often reveals domain-specific problems, such as vocabulary or language that is not commonly used by that group of users. Sometimes user testing can be difficult or expensive, so discount techniques such as heuristic evaluation [2], where evaluators compare the interface with a list of recommended rules of thumb, may be used. Other discount techniques include cognitive walkthrough in which an evaluator role-plays the part of a user trying to complete a task. These techniques may be applied to functional interfaces, to paper prototypes, or other mockups of the interface.
A common method to help designers is the development of user personas, written profiles of fictitious individuals who are designed to be representative of the site's intended users. These individuals' requirements are then used to inform the design process and to guide the design process.
Conclusions
Considering the usability of a web site not only helps users, but also tends to improve the popularity of the site in general. Visitors are likely to get a better impression from usable sites. Quick and simple techniques such as heuristic evaluation can be used to find usability problems; frequent testing of a developing design is ideal, since problems can be found and solved early on. Several methods of usability testing can be used to expose different types of usability problems.
References And Further Information
- Usability 101: Introduction to Usability, J. Nielsen,
<http://hcibib.org/tcuid/chap-4.html> - Heuristic Evaluation, J. Nielsen,
<http://portal.acm.org/citation.cfm?id=142869>
- Ten Usability Heuristics, J. Nielsen,
<http://www.useit.com/papers/heuristic/heuristic_list.html> - Personas: Matching a design to the users' goals,
<http://www.uie.com/articles/personas/>
