What is the role of usability testing in preventing use errors for assistive devices?

• A. It primarily evaluates visual design aesthetics.
• B. It determines manufacturing cost targets.
• C. It measures battery life and charging time.
• D. It reveals user difficulties, ensures tasks can be performed safely and effectively by intended users, and informs design iterations.

Answer: (D)

Usability testing focused on real users reveals where people struggle and what use errors actually occur. In assistive devices, this means watching how intended users perform typical tasks, where they stumble, press the wrong control, misinterpret feedback, or encounter unsafe steps. By uncovering these difficulties, you can verify that tasks can be performed safely and effectively, which is the core goal for preventing use errors. The findings then drive design iterations—refining controls, feedback, labeling, and instructions—until error rates drop and safety improves. Aesthetic appeal, cost targets, or battery life don’t directly address how users interact with the device or prevent safety-related mistakes, so they’re not the primary focus of usability testing aimed at preventing use errors.