## 3 Results and Discussion
### Statistical Analysis of Group Differences
#### 3.3.3 Mann-Whitney U Test Results
For explosion prevention performance, there was a significant difference between the robot operator group and the safety management expert group in severity (\(p\) = 0.007). For unauthorized access, there was a significant difference between the academic experts and the other two groups in terms of the probability of occurrence and a significant difference between the robot operator group and the safety management experts in terms of severity (\(p\) = 0.007). A U value of zero for all significant comparisons means that every rank in one group was higher or lower than every rank in the other group. This suggests that there is a very large difference in perceptions between the groups. It shows that the academic expert group tends to rate most risks higher than the other groups. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Group Comparison** & **U** & \(p\) &
\begin{tabular}{c} **Significance (\(\alpha\) =** \\ **0.0083**) \\ \end{tabular} \\ \hline Group 1 vs. Group 2 & 12.5 & 0.841 & Not significant \\ Group 1 vs. Group 3 & 13 & 0.754 & Not significant \\ Group 1 vs. Group 4 & 0 & 0.007 & Significant \\ Group 2 vs. Group 3 & 8 & 0.485 & Not significant \\ Group 2 vs. Group 4 & 0 & 0.007 & Significant \\ Group 3 vs. Group 4 & 0 & 0.014 & Not significant (after \\  & & & & correction) \\ \hline \hline \end{tabular} Note: Significance is determined based on the Bonferroni-corrected alpha level of 0.0083.  
\end{table} 
Table 6: Results of Mann-Whitney U test for collision (severity). \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Risk Factor** & **Measure** & **Group Comparison** & **U** & **Z** & \(p\) & **Effect Size (r)** \\ \hline \multirow{3}{*}{Collision} & \multirow{3}{*}{Severity} & Group 1 vs. Group 4 & 0 & \(-\)2.68 & 0.007 & 0.85 \\  & & Group 2 vs. Group 4 & 0 & \(-\)2.68 & 0.007 & 0.85 \\  & & Group 3 vs. Group 4 & 0 & \(-\)2.22 & 0.026 & 0.74 \\ \hline \multirow{3}{*}{Collision} & \multirow{3}{*}{Risk Score} & Group 1 vs. Group 4 & 0 & \(-\)2.68 & 0.007 & 0.85 \\  & & Group 2 vs. Group 4 & 0 & \(-\)2.68 & 0.007 & 0.85 \\  & & Group 3 vs. Group 4 & 0 & \(-\)2.22 & 0.026 & 0.74 \\ \hline \multirow{3}{*}{Path Deviation} & \multirow{3}{*}{Severity} & Group 1 vs. Group 4 & 0 & \(-\)2.68 & 0.007 & 0.85 \\  & & Group 2 vs. Group 4 & 0 & \(-\)2.68 & 0.007 & 0.85 \\  & & Group 3 vs. Group 4 & 0 & \(-\)2.22 & 0.026 & 0.74 \\ \hline \multirow{3}{*}{Path Deviation} & \multirow{3}{*}{Risk Score} & Group 1 vs. Group 4 & 0 & \(-\)2.68 & 0.007 & 0.85 \\  & & Group 2 vs. Group 4 & 0 & \(-\)2.68 & 0.007 & 0.85 \\  & & Group 3 vs. Group 4 & 0 & \(-\)2.22 & 0.026 & 0.74 \\ \hline \multirow{3}{*}{Explosion Prevention Performance} & \multirow{3}{*}{Severity} & Group 1 vs. Group 2 & 0 & \(-\)2.68 & 0.007 & 0.85 \\  & & Group 1 vs. Group 4 & 0 & \(-\)2.68 & 0.007 & 0.85 \\ \cline{1-1}  & & Group 2 vs. Group 4 & 0 & \(-\)2.68 & 0.007 & 0.85 \\ \cline{1-1}  & & Group 3 vs. Group 4 & 0 & \(-\)2.22 & 0.026 & 0.74 \\ \hline \multirow{3}{*}{Unauthorized Access} & \multirow{3}{*}{Probability} & Group 1 vs. Group 2 & 0 & \(-\)2.68 & 0.007 & 0.85 \\ \cline{1-1}  & & Group 2 vs. Group 4 & 0 & \(-\)2.68 & 0.007 & 0.85 \\ \cline{1-1}  & & Group 3 vs. Group 4 & 0 & \(-\)2.22 & 0.026 & 0.74 \\ \hline \multirow{3}{*}{Unauthorized Access} & \multirow{3}{*}{Severity} & Group 1 vs. Group 2 & 0 & \(-\)2.68 & 0.007 & 0.85 \\ \cline{1-1}  & & Group 1 vs. Group 4 & 0 & \(-\)2.68 & 0.007 & 0.85 \\ \cline{1-1}  & & Group 2 vs. Group 4 & 0 & \(-\)2.68 & 0.007 & 0.85 \\ \cline{1-1}  & & Group 3 vs. Group 4 & 0 & \(-\)2.22 & 0.026 & 0.74 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Summary of Mann–Whitney U test results significant group differences. These results suggest that the perception of risk factors varies considerably across expert groups, reflecting the impact of each group's expertise and experience on risk assessment.