Universal usability engineering
- 2. USABILITY ENGINEERING Usability engineering is a field that is concerned generally with human-computer interaction and specifically with devising human-computer interfaces that have high usability or user friendliness. It provides structured methods for achieving efficiency and elegance in interface design. Usability engineering is a professional discipline that focuses on improving the usability of interactive systems. It draws on theories from computer science and psychology to define problems that occur during the use of such a system. Usability engineering involves the testing of designs at various stages of the development process, with users or with usability experts.
- 3. History The history of usability engineering in this context dates back to the 1980s. In 1988, authors John Whiteside and John Bennett—of Digital Equipment Corporation and IBM, respectively—published material on the subject, isolating the early setting of goals, iterative evaluation, and prototyping as key activities. The usability expert Jakob Nielsen is a leader in the field of usability engineering. In his 1993 book Usability Engineering, Nielsen describes methods to use throughout a product development process—so designers can ensure they take into account the most important barriers to learnability, efficiency, memorability, error-free use, and subjective satisfaction before implementing the product. Nielsen’s work describes how to perform usability tests and how to use usability heuristics in the usability engineering lifecycle. Ensuring good usability via this process prevents problems in product adoption after release.
- 4. Usability Usability is a quality attribute that assesses how easy user interfaces are to use. The word "usability" also refers to methods for improving ease-of-use during the design process. Usability is defined by 5 quality components: 1. Learnability 2. Efficiency 3. Memorability 4. Errors 5. Satisfaction
- 5. Usability Components Learnability ◦ Ease of learning the system, i.e. the basic tasks ◦ Skills retained over time (also Memorability) Throughput (also Efficiency) ◦ Speed of task performance ◦ Low user error rate Flexibility ◦ Suitability for intended user expertise ◦ Can system be customised? Attitude (also Satisfaction) ◦ User subjective satisfaction with system
- 6. Usability Components (Dimensions of usability) Learnability: How easy is it for users to accomplish basic tasks the first time they encounter the design? Efficiency: Once users have learned the design, how quickly can they perform tasks? Memorability: When users return to the design after a period of not using it, how easily can they reestablish proficiency? Errors: How many errors do users make, how severe are these errors, and how easily can they recover from the errors? Satisfaction: How pleasant is it to use the design?
- 7. Why Usability Is Important On the Web, usability is a necessary condition for survival. If a website is difficult to use, people leave. If the homepage fails to clearly state what a company offers and what users can do on the site, people leave. If users get lost on a website, they leave. If a website's information is hard to read or doesn't answer users' key questions, they leave. Note a pattern here? There's no such thing as a user reading a website manual or otherwise spending much time trying to figure out an interface. There are plenty of other websites available; leaving is the first line of defense when users encounter a difficulty. The first law of ecommerce is that if users cannot find the product, they cannot buy it either. Current best practices call for spending about 10% of a design project's budget on usability.
- 8. How to Improve Usability There are many methods for studying usability, but the most basic and useful is user testing, which has 3 components: •Get hold of some representative users, such as customers for an ecommerce site or employees for an intranet (in the latter case, they should work outside your department). •Ask the users to perform representative tasks with the design. •Observe what the users do, where they succeed, and where they have difficulties with the user interface. Shut up and let the users do the talking.
- 9. When to Work on Usability Usability plays a role in each stage of the design process. The resulting need for multiple studies is one reason I recommend making individual studies fast and cheap. Here are the main steps: Before starting the new design, test the old design to identify the good parts that you should keep or emphasize, and the bad parts that give users trouble. Unless you're working on an intranet, test your competitors' designs to get cheap data on a range of alternative interfaces that have similar features to your own. (If you work on an intranet, read the intranet design annual to learn from other designs.) Conduct a field study to see how users behave in their natural habitat. Make paper prototypes of one or more new design ideas and test them. The less time you invest in these design ideas the better, because you'll need to change them all based on the test results. Refine the design ideas that test best through multiple iterations, gradually moving from low-fidelity prototyping to high-fidelity representations that run on the computer. Test each iteration. Inspect the design relative to established usability guidelines whether from your own earlier studies or published research. Once you decide on and implement the final design, test it again. Subtle usability problems always creep in during implementation.
- 10. The 5E’s to Usability Easy to learn ◦ Supports initial learning and continued learning Efficient ◦ The speed in which users complete their tasks Error tolerant ◦ The ability of the interface to prevent errors or help users recover from those that occur Effective ◦ The completeness and accuracy with which users achieve their goals Engaging ◦ How pleasant or satisfying the interface is to use?
- 11. Some metrics from ISO 9241 Usability Effectiveness Efficiency Satisfaction objective measures measures measures Suitability Percentage of Time to Rating scale for the task goals achieved complete a task for satisfaction Appropriate for Number of power Relative efficiency Rating scale for trained users features used compared with satisfaction with an expert user power features Learnability % of functions Time to learn Rating scale for learned criterion ease of learning Error tolerance % of errors Time spent on Rating scale for corrected successfully correcting errors error handling