## 3 Results and Discussion
### Statistical Analysis of Group Differences
#### 3.3.2 Kruskal-Wallis Test Results  
The Kruskal-Wallis test was performed to analyze the differences in perceptions of risk factors for quadruped robots between groups of experts. The purpose of this test is to test for differences in the distribution of a particular risk factor assessment between three or more groups. The null hypothesis (H0) for the research question is that there is no difference in the distribution of the risk factor assessment between the expert groups, while the alternative hypothesis (H1) is that the distribution of the assessment of at least one group differs from the other groups. Below is Table 5, which shows the average ranking of the groups by risk factor and the results of the Kruskal-Wallis test. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Risk Factor**} & \multirow{2}{*}{**Measure**} & \multicolumn{2}{c}{**Kolmogorov–Smirnov***} & \multicolumn{2}{c}{**Shapiro–Wilk**} \\ \cline{3-6}  & & **Statistic** & \(p\) & **Statistic** & \(p\) \\ \hline \multirow{2}{*}{Work environment} & Severity & 0.199 & 0.045 & 0.899 & 0.046 \\  & Probability & 0.202 & 0.039 & 0.836 & 0.004 \\ \hline \multirow{2}{*}{Unauthorized access} & Severity & 0.208 & 0.03 & 0.822 & 0.002 \\  & Probability & 0.381 & \textless{}0.001 & 0.696 & \textless{}0.001 \\ \hline \multirow{2}{*}{External acceleration} & Severity & 0.282 & \textless{}0.001 & 0.821 & 0.002 \\  & Probability & 0.328 & \textless{}0.001 & 0.715 & \textless{}0.001 \\ \hline \multirow{2}{*}{Other} & Severity & 0.255 & 0.002 & 0.893 & 0.037 \\  & Probability & 0.255 & 0.002 & 0.873 & 0.016 \\ \hline \hline \end{tabular} Degree of freedom = 19. * Lilliefors significance correction.  
\end{table} 
Table 4: _Cont._ \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Risk Factor**} & \multirow{2}{*}{**Measure**} & \multicolumn{2}{c}{**Group 1**} & \multicolumn{2}{c}{**Group 2**} & \multicolumn{2}{c}{**Group 3**} & \multicolumn{2}{c}{**Group 4**} & \multicolumn{2}{c}{**Kruskal–Wallis Test Results**} \\ \cline{3-8}  & & **Mean Rank** & **Mean Rank** & **Mean Rank** & **Mean Rank** & **\(H\)** & **df** & \(p\) \\ \hline \multirow{3}{*}{Collision} & Severity & 9.4 & 8.4 & 8.5 & 13.4 & 2.884 & 3 & 0.41 \\  & Probability & 8.9 & 7.7 & 6.75 & 16 & 8.734 & 3 & 0.033 \\  & RiskScore & 8.8 & 8.6 & 5.38 & 16.3 & 9.78 & 3 & 0.021 \\ \hline \multirow{3}{*}{Path deviation} & Severity & 11.7 & 7 & 6.5 & 14.1 & 6.417 & 3 & 0.093 \\  & Probability & 6.6 & 10.6 & 5 & 16.8 & 13.554 & 3 & 0.004 \\  & RiskScore & 8.7 & 8.4 & 5.75 & 16.3 & 9.351 & 3 & 0.025 \\ \hline \multirow{3}{*}{Battery discharge} & Severity & 8.6 & 11.6 & 8.25 & 11.2 & 1.529 & 3 & 0.676 \\  & Probability & 14.5 & 3.8 & 8.13 & 13.2 & 13.368 & 3 & 0.004 \\ \cline{1-1}  & RiskScore & 11.5 & 7 & 8.63 & 12.6 & 3.183 & 3 & 0.364 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Mean rank by risk factor and Kruskal–Wallis test results. The test results revealed statistically significant differences in perception among expert groups for several risk factors:  
* Collision: probability (H = 8.734, \(p\) = 0.033) and risk score (H = 9.780, \(p\) = 0.021);
* Path deviation: probability (H = 13.554, \(p\) = 0.004) and risk score (H = 9.351, \(p\) = 0.025);
* Battery discharge: probability (H = 13.368, \(p\) = 0.004);
* Explosion prevention performance: severity (H = 8.161, \(p\) = 0.043);
* Unauthorized access: probability (H = 8.293, \(p\) = 0.040), severity (H = 9.153, \(p\) = 0.027), and risk score (H = 8.856, \(p\) = 0.031). These results are all statistically significant at the \(p\) < 0.05 level, objectively demonstrating the differences in perception of various risk factors among expert groups. Examination of the mean rankings shows that academic experts (Group 4) generally tended to assess risks higher than other groups, a pattern that is visually confirmed by both the heatmap (Figure 2(b)) and spider diagram (Figure 4).