# The Effects of Augmented Reality Companion on User Engagement in Energy Management Mobile App
## 5 Discussion
### System Usability Scale and Perceived Usability  
The SUS scores are expressed as percentiles rather than percentages. The average SUS scores of the TUI and ARUI by Group A (TUI: 84.17, ARUI: 78.13) and B (TUI: 69.00, ARUI: 72.00) participants were above 68. Therefore, both UIs of our mobile apps were considered to provide more than average experience since a commonly accepted average SUS score representing average experience is 68 [52]. We found that SUS of the ARUI by Group A had no statistically significant increase from the TUI (Table 6). In fact, there was a significant decrease of SUS in the ARUI compared to the TUI \(t(23)=-2.35\), \(p=0.01\), CI [\(-10.45\), \(-1.64\)], and Figure 7 showed that only six participants in Group A perceived better usability in the ARUI over TUI. One dimension, PU, in the UES presented a similar result, which was a negative effect. We identified a significant decrease in the ARUI from TUI at PU of UES, \(t(23)=-2.52\), \(p=0.01\), CI [\(-0.49\), \(-0.09\)]. In addition, we checked Group B's SUS and UES scores to find the characteristics of their results. Three out of five participants in Group B rated higher scores for the TUI than the ARUI in SUS, and Group B's UES data showed that the TUI in PU achieved a higher value than the ARUI. Although Group B's mean SUS score of ARUI (M = 72.00, SD = 14.83) was higher than the TUI (M = 69.00, SD = 26.80), we presume that [PERSON]'s SUS score is an outlier that distorted the result of Group B. The potential reasons for [PERSON]'s SUS score could be the difficulties that [PERSON] faced during the TUI evaluation. For example, during the TUI evaluation, we lent [PERSON] a tablet PC with a much larger display than a smartphone for better readability and easy control with relatively large-size buttons. However, experiencing the PHOENIX solution through the TUI was still a tough task for [PERSON] due to physical constraints caused by aging (age \(70\leq\) P29). Multiple text readings and room temperature controls with finger touches were a burden to [PERSON]. Due to body movement difficulty, [PERSON] was issued interacting with the AR companion using her hands. This issue was observed from other participants as well. We assume this issue negatively affected the perceived usability of the ARUI. However, despite an obstacle caused by a limited physical ability, we observed that [PERSON] enjoyed interacting with the AR companion once [PERSON] successfully summoned it. The user behavior-based reactions that the AR companion showed left a favorable impact on her. Moreover, the AR companion's room temperature-based animation appealed to her because she could quickly obtain high-level information about room conditions by watching the AR companion. Apart from the AR companion, [PERSON] preferred the audio output in the ARUI since she could obtain the information by listening instead of reading. [PERSON]'s case reminds us of the importance of multimodality in supporting various user contexts [53; 54]. Regarding the low SUS scores of the ARUI compared to TUI from other participants in both groups, we assume the discomfort, which was caused by physical constraints of aging in hand alignment for using AR, affected the results since perceived usability was influenced by inconvenience. The participants needed to keep one of their hands in the air to spawn the AR companion while holding a mobile device in another hand, and the participants in Group B (age M = 73.40) were hardly able to do both in a stable condition. Even in a simple task, such as positioning the palm towards the mobile device's camera, the participants suffered from a shaky hand, resulting in instability of the AR companion initialization. Another case was the inconvenience of moving and stretching their arms to find a proper distance between the mobile device and their hand for good positioning of the AR companion.