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Usability engineering is a field that is concerned generally with human-computer interaction and specifically with making human-computer interfaces that have high usability or user friendliness. In effect, a user-friendly interface is one that allows users to effectively and efficiently accomplish the tasks for which it was designed and one that users rate positively on opinion or emotional scales. Assessing the usability of an interface and recommending ways to improve it is the purview of the Usability Engineer. The largest subsets of Usability Engineers work to improve usability of software graphical user interfaces (GUIs), web-based user interfaces, and voice user interfaces (VUIs).
Several broad disciplines including Psychology, Human Factors and Cognitive Science subsume usability engineering, but the theoretical foundations of the field come from more specific domains: human perception and action; human cognition; behavioral research methodologies; and, to a lesser extent, quantitative and statistical analysis techniques.
When usability engineering began to emerge as a distinct area of professional practice in the mid- to late 1980s, many usability engineers had a background in Computer Science or in a sub-field of Psychology such as Perception, Cognition or Human Factors. Today, these academic areas still serve as springboards for the professional practitioner of usability engineering, but Cognitive Science departments and academic programs in Human-Computer Interaction now also produce their share of practitioners in the field.
The term usability engineering (in contrast to interaction design and user experience design) implies more of a focus on assessing and making recommendations to improve usability than it does on design, though Usability Engineers may still engage in design to some extent, particularly design of wire-frames or other prototypes.
Standards and guidelines 
Usability engineers sometimes work to shape an interface such that it adheres to accepted operational definitions of user requirements. For example, the International Organisation for Standardisation-approved definitions (see e.g., ISO 9241 part 11) usability are held by some to be a context-dependent yardstick for the effectiveness, efficiency and satisfaction with which specific users should be able to perform tasks. Advocates of this approach engage in task analysis, then prototype interface design, and usability testing on those designs. On the basis of such tests, the technology is (ideally) re-designed or (occasionally) the operational targets for user performance are revised. [Dillon, 2000].
The National Institute of Standards and Technology has collaborated with industry to develop the Common Industry Specification for Usability - Requirements, which serves as a guide for many industry professionals. The specifications for successful usability in biometrics were also developed by the NIST. Usability.Gov provides a tutorial and wide general reference for the design of usable websites.
Usability, especially with the goal of Universal Usability, encompasses the standards and guidelines of design for accessibility. The aim of these guidelines is to facilitate the use of a software application for people with disabilities. Some primary guidelines for web accessibility are:
- The Web Accessibility Initiative Guidelines
- The Section 508 government guidelines applicable to all public-sector websites.
- The ADA Guidelines for accessibility of state and local government websites.
- The IBM Guidelines for accessibility of websites.
Methods and tools 
Usability Engineers conduct usability evaluations of existing or proposed interfaces and their findings are fed back to the Designer for use in design or redesign. Common usability evaluation methods include:
- usability testing (Gold standard of Usability Engineering, but the most involved and expensive method)
- focus groups
- cognitive walkthroughs
- heuristic evaluations
- RITE method
- cognitive task analysis
- contextual inquiry
- Think aloud protocol
Usability testing, the gold standard, is when participants are recruited and asked to use the actual or prototype interface and their reactions, behaviors, errors, and self-reports in interviews are carefully observed and recorded by the Usability Engineer. On the basis of this data, the Usability Engineer recommends interface changes to improve usability.
There are a variety of online resources that make the job of the Usability Engineer a little easier. Some examples of these include:
1. The Web Metrics Tool Suite is a product of the National Institute of Standards and Technology. This toolkit is focused on evaluating the HTML of a website versus a wide range of usability guidelines and includes:
- Web Static Analyzer Tool (WebSAT) - checks web page HTML against typical usability guidelines
- Web Category Analysis Tool (WebCAT) - lets the usability engineer construct and conduct a web category analysis
- Web Variable Instrumenter Program (WebVIP) - instruments a website to capture a log of user interaction
- Framework for Logging Usability Data (FLUD) - a file format and parser for representation of user interaction logs
- FLUDViz Tool - produces a 2D visualization of a single user session
- VisVIP Tool - produces a 3D visualization of user navigation paths through a website
- TreeDec - adds navigation aids to the pages of a website
consists of two tightly-integrated applications. The first is the UTE Manager, which helps a tester set up test scenarios (tasks) as well as survey and demographic questions. The UTE Manager also compiles the test results and produces customized reports and summary data, which can be used as quantitative measures of usability observations and recommendations. The second UTE application is the UTE Runner. The UTE Runner presents the test participants with the test scenarios (tasks) as well as any demographic and survey questions. In addition, the UTE Runner tracks the actions of the subject throughout the test including clicks, keystrokes, and scrolling.
It is important to remember that online tools are only a useful tool, and do not substitute for a complete Usability Engineering analysis.
Research resources 
Some well-known practitioners in the field are Donald Norman, Jakob Nielsen, and John M. Carroll. Nielsen and Carroll have both written books on the subject of usability engineering. Nielsen's book is aptly titled Usability Engineering, and was published in 1993. Carroll wrote "Making Use: Scenario-Based Design of Human-Computer Interactions" in 2000, and co-authored "Usability Engineering: Scenario-Based Development of Human-Computer Interaction" with Mary Beth Rossen in 2001. Some other field leaders are Alan Cooper, Larry Constantine and Steve Krug the author of "Don't Make Me Think! A Common Sense Approach to Web Usability".
There are many books written on Usability Engineering. A few of the more popular recently published books are as follows:
- Nielsen, Jakob (1993). Usability engineering. Morgan Kaufmann. p. 362. ISBN 978-0-12-518406-9.
- Spool, Jared; Tara Scanlon, Carolyn Snyder, Terri DeAngelo (1998). Web Site Usability: A Designer's Guide. Morgan Kaufmann. p. 176. ISBN 978-1-55860-569-5.
- Mayhew, Deborah (1999). The Usability Engineering Lifecyle: A Practitioner's Handbook. Morgan Kaufmann. p. 560. ISBN 978-1-55860-561-9.
- Faulkner, Xristine. Usability Engineering. Palgrave. p. 256. ISBN 978-0-333-77321-5.
- Smith, Michael J. (2001). Usability Evaluation and Interface Design: Cognitive Engineering, Intelligent Agents, and Virtual Reality, Volume 1 (Human Factors and Ergonomics). CRC Press. p. 1592. ISBN 978-0-8058-3607-3.
- Rosson, Mary Beth; John Millar Carroll (2002). Usability Engineering: Scenario-Based Development of Human-Computer Interaction. Morgan Kaufmann. p. 422.
- Jacko, Julie (2012). Human-Computer Interaction Handbook: Fundamentals, Evolving Technologies, and Emerging Applications. CRC Press. ISBN 978-1-4398-2943-1.
- Leventhal, Laura (2007). Usability Engineering: Process, Products & Examples. Prentice Hall. p. 336. ISBN 978-0-13-157008-5.
- Sears, Andrew; Julie A. Jacko (2007). The Human-Computer Interaction Handbook: Fundamentals, Evolving Technologies and Emerging Applications. CRC Press. p. 1384. ISBN 978-0-8058-5870-9.
See also 
- User interface engineering
- User experience design
- Usability testing
- World Usability Day
- Component-Based Usability Testing
- Andrew Dillon. Group dynamics meet cognition: combining socio-technical concepts and usability engineering in the design of information systems (http://dlist.sir.arizona.edu/1282/01/Ad2000.pdf)
- Jakob Nielsen: Usability Engineering. Academic Press, Boston 1993 ISBN 0-12-518405-0
- John M. Carroll: Making Use: Scenario-Based Design of Human-Computer Interactions. MIT Press Cambridge, MA, 2000 ISBN 0-262-03279-1
- Mary Beth Rosson, John M. Carroll: Usability engineering: scenario-based development of human-computer interaction. Morgan Kaufmann Publishers Inc. San Francisco, CA, 2001 ISBN 1-55860-712-9