There are many methodological tools one can use to inform the design of usable tools and interfaces. For simplicity, I’ve sorted these methods into two approaches and four categories that represent phases in the design process. Below is a classic representation of the usability design cycle. I’ve added another line in the spiral to indicate that there are at least two approaches to doing usability design.
Figure 1.0
Full usability methods are those that involve many users (as many as can be considered optimal to find a majority of usability problems) and can take anywhere from several weeks to months of research and design work. These methods are ideal for situations where one has a high level of access to a population of representative users and where one has several weeks to months of time to plan and execute user studies.
Discount usability methods are often used when time is scarce (such as in Agile-based development environments) or when access to users may be limited. In these situations, working with as few as 5 users is often enough to identify the majority of usability issues.
(to be continued…)