## 4 Results
### Analysis of the Questionnaire Data
A single asterisk (*) denotes a \(p\)-value less than 0.05, while three (**) asterisks denote \(p\)-values less than 0.001, respectively. Figure 9: A graph that compares trust, perceived safety, immersion and presence, and situation awareness questionnaire data according to risk level and whether or not information was provisioned through HUD. The use of asterisks in the figure indicates statistical significance. A single asterisk (*) denotes a \(p\)-value less than 0.05, while two (**) and three (***) asterisks denote \(p\)-values less than 0.01 and 0.001, respectively. Through the reaction to the events questionnaire, we found that there was a significant difference in the degree of risk perceived by the subjects according to the risk level and that the degree of awareness of the upcoming risk significantly increased when information was provided to HUD. In the case of reaction questionnaire 1, the high-risk condition was significantly higher than the medium-risk (\(p<0.001\)), low-risk (\(p<0.001\)), and no-risk (\(p<0.001\)) conditions and the medium-risk condition was significantly higher than the low-risk (\(p<0.05\)) and no-risk (\(p<0.001\)) conditions and the low-risk condition was significantly higher than the no-risk condition (\(p<0.001\)). In the case of reaction questionnaire 2, the high-risk condition was significantly higher than the medium-risk condition (\(p<0.001\)), low-risk condition (\(p<0.001\)), and no-risk condition (\(p<0.001\)), and the medium-risk condition was significantly higher than the low-risk condition (\(p<0.001\)) and the no-risk condition (\(p<0.001\)), and the low-risk condition was significantly higher than the no-risk condition (\(p<0.001\)). In the case of reaction questionnaire 3, the high-risk condition was significantly lower than the low-risk (\(p<0.001\)) and no-risk conditions (\(p<0.01\)), and the medium-risk condition was significantly higher than the low-risk (\(p<0.001\)) and no-risk conditions (\(p<0.001\)). In addition, when information was provided, the value was significantly higher than when the information was not provided (\(p<0.001\)). The score of reaction questionnaire 4 was significantly higher when the information was provided than when the information was not provided (\(p<0.001\)). For post-questionnaire 1-4, we confirmed the significance using ANOVA. Except for the significance between high-risk and no-risk conditions (\(p<0.05\)), there was no significant difference between risk levels, but the value decreased slightly from question 1 to question 4 (Figure 11 Left): F(3, 176) = 3.727, (\(p<0.05\)). For post-questionnaire 5-6, we confirmed the significance using the Wilcoxon signed-rank test. The value for question 5 was significantly higher than that for question 6 (\(Z=3.677\), \(p<0.001\)) (Figure 11 Right). Through post questions 1-4, we found that the higher the risk, the more the subject felt safe about providing information to the HUD. In addition, through post questions 5-6, we found that as the risk level increased, information provided on the HUD increased the trust in autonomous vehicles, while not information provided on the HUD decreased the trust. In other words, we could infer that information provided on the HUD had a positive effect on the user experience of autonomous vehicles. Figure 11: A graph that compares post-questionnaire data according to risk level and whether to provide information to HUD or not. The use of asterisks in the figure indicates statistical significance. A single asterisk (*) denotes a \(p\)-value less than 0.05, while three (***) asterisks denote \(p\)-values less than 0.001, respectively.