## 5 Experiment 2
### Design  
The experiment was conducted in a demonstration room, which was designed as a living room with a size of about 4 \(\times\) 3 \(\times\) 8 m (width, height, depth) in shown as Figure 5a. Since we assume that HMD and AR Pointer are mainly used indoors, we cut off outdoor lighting with blinds and experimented in the lighting environment where only indoor fluorescent lamps are affected. The subjects consisted of 21 people ranging in age from 24 to 31 (mean [M] + standard deviation [SD] = 27.4 + 2.5, male = 15, female = 6) and one subject was left-handed. Eight of them had experience with head-mounted display HMD-based AR. Participants were briefed about the HoloLens and two methods and given time to practice these techniques. The duration of the exercise session was finished when the subjects were well-informed and those without HMD-based AR experience took somewhat longer (up to 10 min, about 5 min on average). In the case of the HoloLens interface, the default method in which the GaS and wireframe methods are used, was chosen for the second experiment in shown as Figure 6. The AR Pointer is used to perform the task through object manipulation method as proposed in Section 3.2. Figure 5: Experiment 2 test environment. (**a**) Demonstration room overview. (**b,c**) Docking tasks of 3D objects using AR Pointer. When the experiment was started, three dummy (ground truth) objects in the form of a cube was created in which the ground truth (GT) positions in specified positions in the room were placed. After a few seconds, experimental objects were created at another location and the user performed four tasks (selection, translation, rotation, scaling) so that the experimental objects overlaps with the GT object. The distances between the three sets of experimental objects and GT objects were set to 2.5, 4.5 and 6.5 m, respectively. These operations can be performed in the order chosen by the user. This task was performed six times by each user (2 interfaces \(\times\) 3 target positions). Every time a task is completed (designated as the time when the users feel finished and the volume of unions \(>\) 90%), it measures the task completion time and the error rate between the two objects. The experiment took an average of 19.2 min per person. After the task completion time experiment, we conducted two surveys to obtain a subjective assessment of the subjects. One is the system usability scale (SUS) [30] for comparing the usability of the two interfaces and the other is the NASA task load index (NASA-TLX) [31; 32] for comparing the fatigue when using both interfaces. Both questionnaires are standard questionnaires frequently used in human-computer interaction (HCI) and are listed in Tables 1 and 2. The [PERSON]'s alpha [33] value for questionnaires reliability is \(\alpha>\) 0.9 [34] for SUS and \(\alpha>\) 0.7 [35; 36; 37] for NASA-TLX. [PERSON]'s alpha \(\alpha>\) 0.7, it was accepted as a questionnaire [38]. In the survey using SUS qestionnaire, the users answered questions in ten categories about each AR interface. A 7-point Likert scale was used in this survey. In the case of this questionnaire, it is designed to alternate positive and negative questions in order to prevent accidental bias. Each question was answered with a score between 1 and 7 (indicating strongly disagree and strongly agree, respectively). We also conducted a short interview concerning subjective comments about these interfaces. The NASA-TLX survey consists of two parts. First of all, the subjects fill in the score of 5 point steps within the range of 100 points for 6 questions. Next, the subjects will group all six items together and conduct a 15-pair comparison. The subjects conducted a 15-pair comparison of the question \"When designing the interface to be used in HoloLens, which of the two items should be considered more?\". We also accumulated the selected responses to get the weighted scores. The weighted scores thus obtained was used as the workload weight when obtaining the total fatigue score from each NASA-TLX result.