# Development of Low-Fidelity Virtual Replicas of Products for Usability Testing
## 4 Materials and Methods
### Product and Use Case Scenario  
A real world device and use case scenario was selected to demonstrate the process of designing a virtual product with the ability to push buttons, move objects, and receive sensory cues. To test this approach in the general population, it was necessary to select a product that required minimal formal training and could be used by the general population, thereby allowing for more flexibility in recruiting subjects for the pilot study described later in this paper. Automated external defibrillators (AED) were selected for this purpose as minimal training is required, and these devices can be found in many public areas, such as airports and hotels. AEDs are medical devices that attempt to restore normal heart rhythm in people who have suffered from sudden cardiac arrest (SCA) [68]. Due to the increase in people suffering from SCA outside of hospitals, semi- to completely automatic AEDs have been created for public use [68; 69]. These devices are designed to be used by individuals without formal medical training, typically requiring a short certification course (e.g., half day course) to operate the device.  
Despite the minimal training requirements, studies have shown that people struggle to use AEDs correctly for several reasons such as not hearing the instructions, assuming thatthe device can only be used by trained personnel, and misunderstanding where to place the shock pads, among other issues [70,71]. AEDs would benefit from further usability evaluation and design refinement due to the reported use errors and its public health impact. Misuse of this device can lead to an inaccurate assessment of the SCA victim's heart rhythm, or an ineffective shock being delivered, which could result in death.  
Several AEDs were reviewed to aid in developing the simulated use pilot study. A list of common interaction steps were first generated after reviewing user manuals of existing semi-automatic AEDs available on the US market [72, 73, 74, 75, 76, 77]. This served as the basis for the software architecture of the simulation. The steps listed in the user manuals explained expected human interactions, the components of the device that require active (e.g., pushing button) or passive (e.g., viewing flashing light) interaction, and the responses they should receive after performing actions (e.g., a new voice instruction playing). These activities should be replicated in the virtual prototype.  
AEDs are designed to walk users through how to operate them effectively by providing visual and auditory feedback during the individual task and transitions between tasks. The steps that involve passive or active interaction with the AED are summarized in Table 1. The user will start by turning on the device and then proceeding to move objects from the AED to the SCA victim. The user will avati feedback from the AED on what to perform next. An important step in this process is the cycle between the shock analysis step and performing CPR. Shock and CPR deliverance will cycle until there is a notable recovery of breathing from the patient, which will be analyzed during the analysis time of the device. AEDs must be used quickly and effectively to save an SCA victim's life. The SCA victim's chance of survival drops by 10% for every minute of delay [69]. Subjects participating in the low-fidelity usability test will be required to deliver two shocks and rounds of CPR to a simulated SCA victim. For this low-fidelity test, subjects will only perform the steps involving using the AED (Table 1).  
In Table 1, Steps 1 and 5 require the subject to push a button on the device. Steps 2 and 3 require moving device components from one location to another. Lastly, Steps 4 and 6 require the subject to receive sensory feedback. An overview of the essential aspects to be replicated will be discussed in more depth below.