Usability - Investigation

Investigation

The key principle for maximizing usability is to employ iterative design, which progressively refines the design through evaluation from the early stages of design. The evaluation steps enable the designers and developers to incorporate user and client feedback until the system reaches an acceptable level of usability.

The preferred method for ensuring usability is to test actual users on a working system. Although, there are many methods for studying usability, the most basic and useful is user testing, which has three components:

• Get some representative users.
• 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.

It's important to test users individually and let them solve any problems on their own. If you help them or direct their attention to any particular part of the screen, you will bias the test. Rather than running a big, expensive study, it's better to run many small tests and revise the design between each one so you can fix the usability flaws as you identify them. Iterative design is the best way to increase the quality of user experience. The more versions and interface ideas you test with users, the better.

Usability plays a role in each stage of the design process. The resulting need for multiple studies is one reason to make individual studies fast and cheap, and to perform usability testing early in the design process. Here are the main steps:

• Before starting the new design, test the old design to identify good parts you should keep or emphasize, and bad parts that give users trouble.
• Test competitors' designs to get data on a range of alternative designs.
• Conduct a field study to see how users behave in their natural habitat.
• Make mock-ups or 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 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.

Don't defer user testing until you have a fully implemented design. If you do, it will be impossible to fix the vast majority of the critical usability problems that the test uncovers. Many of these problems are likely to be structural, and fixing them would require major rearchitecting. The only way to a high-quality user experience is to start user testing early in the design process, and to keep testing every step of the way.