Certification of usability: a process for creating a human-centered system

If a system or procedure is being developed that will be used by humans, the design should be human-centered. Human-centered design capitalizes on and accommodates human skills in perception, attention, and cognition, while minimizing the opportunities for and effects of human error. This paper describes a mature practical process for accomplishing this goal of human-centered design. Usability is the foundation of this process. The first step in creating a human-centered system is to determine who the operators are, how, where, and what they are using the system for now, and what they would like to use it for in the future. The next step is to set relevant and realistic usability goals for the user interface of the new system. These goals include the time to accomplish the task and error tolerance. The final step is to perform usability testing, starting with a prototype. Many usability issues will become apparent by creating scenarios that 1) exercise a representative sample, if not all, of the operator functions and 2) provide a realistic operational environment for testing. By collecting and analyzing usability data, specific interface features can be evaluated and any mismatch between the design and the operational use will be revealed. Through iterative design improvements the final product will be easy to use and difficult to use incorrectly.