A number of usability methods have been described in the liturature, such as cognitive walkthrough (where evaluations/users systematically document and talk through the goals and steps involved in using the interface), and heuristic evaluation (where usability specialists determine whether each element of a user interface follows established usability principles). An example of rules of thumb for heuristic evaluation of user interfaces comes from Jacob Neison, considered one of the pioneers in the area:

• Visibility of system status.
• Match between system and the real world.
• User control and freedom.
• Consistency and standards.
• Error prevention.
• Recognition rather than recall.
• Flexibility and efficiency of use.
• Aesthetic and minimalist design.
• Help users recognize, diagnose, and recover from errors.
• Help and documentation.

The above is quite general. Here we are especfially interested in usability/ergonomic analysis that targets activities/tasks using devices where the performance goals are clearly identifiable. Often such activities can be broken into a sequence of subtasks (e.g., stages related to positioning, mobility, reaching, manipulation, and communication). Each of these can be broken down further, and there are many such classification schemes. For instance, the RERC-AMI is working on such schemes, and some of these may be presented in class.

Of note is that generally-speaking, observations of performance are not sufficient for task analysis, except for very simple tasks. Sensors and observers simply cannot get into the mind of the user. Normally the usability engineer must also employ methods that extract information from the subject/client, for instance related to their understanding of a product, the choices they made to perform a task, their opinions of a product, and perhaps their suggestions for improvment. Often this takes the form of both a structured questionnaire or interview, and an open-ended stage. Normally such information collection immediately follows performance of the activity. The MU-Lab is an example of such an instrument.

Another perspective comes from the FDA and it's Center for Devices and Radiological Health, which has the responsibility for regulating medical devices (including "durable medical equipment" such as wheelchairs). Considering that the eighth leading cause of death in the U.S. is said to be medical error, and that many homecare/rehabilitation technologies have migrated into the home (often used by persons with functional limitations), the FDA has developed a clear interest in encouraging human factors in medical product design. The FDA's Human Factors Program has produced documents and supported standards activities that provide a different type of "systems" perspective, targeted to help companies minimize user risks and provide error tolerance, including:

• Do it by Design: An Introduction to Human Factors in Medical Devices (by FDA's D. Sawyer, 1996)
• Medical Device Use-Safety: Incorporating Human Factors
  Engineering into Risk Managementay (by FDA's R. Kaye and J. Crowley, 2000)
• AAMI / ANSI HE74-2001 Standard: Human Factors Design Process for Medical Devices

Other important terms, especially for medical products, include realiability, safety and efficacy. Practitioners in particular have little patience for new products that are not immediately reliable.

| overview | terminology | systems-analysis | universal design | task-analysis |