Usability

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This article will be merged or at least coordinated with web usability - Daniel K. Schneider 18:31, 1 February 2011 (CET)

Definition

Usability is a term used to denote the ease with which people can employ a particular tool or other human-made object in order to achieve a particular goal. [...] In human-computer interaction and computer science, usability usually refers to the elegance and clarity with which the user interface of a computer program or a web site is designed. The term is also used often in the context of products like consumer electronics, or in the areas of communication, and knowledge transfer objects (such as a cookbook, a document or online help). It can also refer to the efficient design of a mechanical objects such as a door handle or a hammer. (Wikipedia: Usability - retrieved 17:30, 9 June 2006)

Usability can also refer to the methods of measuring usability and the study of the principles behind an object's perceived efficiency or elegance. (Wikipedia: Usability - retrieved 17:30, 9 June 2006 )

In more practical terms. ISO links usability to effectiveness, efficiency, and satisfaction, for a given product in a given context. According to the on-line Technical Layout & Design course (Technical Expressions, Inc,)

Usability specialists have expanded the ISO definition of usability, stating that a usable product is:

  • easy to learn
  • efficient to use
  • provides quick recovery from errors
  • easy to remember
  • enjoyable to use
  • visually pleasing

, retrieved 17:13, 26 January 2011 (CET).

See also:

Design and usability methods

Usability is a factor in all design stages (e.g. requirements, design, implementation, testing, evaluation). I.e. usability guidelines are considered early in the process and early design prototypes like wireframes are also subject to usability testing.

Usability testing happens mostly in (re)design and testing phases. Wikipedia summarizses the goals of usabilit testing as follows:

of improvement. Usability testing generally involves measuring how well test subjects respond in four areas: efficiency, accuracy, recall, and emotional response. The results of the first test can be treated as a baseline or control measurement; all subsequent tests can then be compared to the baseline to indicate improvement.

  • Performance -- How much time, and how many steps, are required for people to complete basic tasks? (For example, find something to buy, create a new account, and order the item.)
  • Accuracy -- How many mistakes did people make? (And were they fatal or recoverable with the right information?)
  • Recall -- How much does the person remember afterwards or after periods of non-use?
  • Emotional response -- How does the person feel about the tasks completed? Is the person confident, stressed? Would the user recommend this system to a friend?
(retrieved 14:16, 11 March 2011 (CET))

It is important to understand that good usability testing is not asking for opinions like "do you like the system", "can you understand X", but giving persons carefully crafted tasks to do. Typically, such user sessions are recorded and/or monitored by observers and then analysed in detail. However, more lighweight methods do exist and some dimensions of usability (e.g. user experience/emotional response/satisfaction) may be measured by questionnaires.

See Design and usability methods and techniques for more details.

Usability measures

The ISO dimensions of efficiency, effectiveness and satisfaction can be operationalized in various ways: Sauro and Kindlund, (2005), in their SUM index use a mean of four (standardized) measures:

  • efficiency is measured through task times
  • effectiveness is measured both through number of errors and task completion
  • satisfaction is measured with a short questionnaire based on Lewis (1991).

In other words, the SUM index can be summarized as: 

usability = 0.25 * z-score (task time)
          + 0.25 * z-score-equivalent (N erros)
          + 0.25 * z-score-equivalent (task completion)
          + 0.25 * z-score (satisfaction)

Usability and innovation

“People tend to gravitate to what they are used to and usability is mainly concerned with that: whether or not a product responds in an expected way. If everything acts as expected, then many fewer innovations would be made.” IXDA discussion (retrieved March 2011).

This sort of argument probably helped establishing user experience research as one way of doing design research. Another rationale for more "experience"-oriented research was formulated by by Marc Hassenzahl: “This is the challenge designers and vendors of interactive products face: Experience or User Experience is not about good industrial design, multi-touch, or fancy interfaces. It is about transcending the material. It is about creating an experience through a device. [...]”. He also points out, that there is a shit in Western societies from the material to the experiential and technology-oriented businesses have potential problems in accommodating this shift. (retrieved March,4 2010)

Links

Resources

Larger usability sites (randomly sorted). Most include lot's of interesting materials.

General introductions

See also web usability and user interaction and user interface design

The US Research-Based Web Design & Usability Guidelines

“Throughout your Web design or redesign project, you should take advantage of what is already known about best practices for each step of the process. The Research-Based Web Design and Usability Guidelines, compiled through an extensive process of research and review, bring you those best practices.”

Various interesting pieces
  • User in Your Face, The Student Programmer's Before-and-After Guide to Usability and Usable Interface Design, by Jack Bellis.
Propaganda videos
On Wikipedia

You may start from the Desing portal, a page that indexes most pages related to design including usability.

Sample pages:

Usability methods and tools

See Design and usability methods and techniques

Government

Standards

  • ISO/TR 16982:2002 - "Ergonomics of human-system interaction—Usability methods supporting human-centered design"
  • ISO 9241 - "Ergonomics of Human System Interaction" -

References

See Interaction design, user experience and usability for a bibliography.

  • Lewis, J. R. (1991). Psychometric evaluation of an afterscenario questionnaire for computer usability studies: The ASQ. SIGCHI Bulletin, 23, 78-81.
  • Sauro, Jeff and Erika Kindlund, (2005). A Method to Standardize Usability Metrics into a Single Score, CHI 2005, PDF reprint
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