## 3 Results
### Correlation Coefficients and Regression Analysis  
Table 6 shows the correlation coefficients between USD guidelines and the mean of UD. According to the correlation coefficient between the USD guidelines, physical support (S1) was the highest relationship with accessibility (0.635). The flexibility (S2) was the highest correlation coefficient with diversity and inclusion (0.637), while accessibility (S3) was the highest relationship with ensuring safety and health (0.690). Ensuring safety and health (S4) was the highest relationship with sustainability (0.697), and diversity and inclusion (S5) was the highest relationship with accessibility (0.654).  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Observed Variables** & **Factor** \\ \hline U3 Simplicity & 0.813 \\ U7 Appropriate size and space & 0.808 \\ U5 Error-proof design & 0.746 \\ U1 Equitable use & 0.744 \\ U6 Low physical effort & 0.737 \\ U2 Flexible design & 0.716 \\ U4 Perceptibility & 0.695 \\ Explained total variance = 56.6\% \\ Kaiser–Meyer–Olkin test = 0.860 \\ Bartlett test \(\chi^{2}\) = 486.9, \(p\) \(<\) 0.001 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Results of factor analysis on UD guidelines.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Factor Analysis by USD Guidelines** & **Factor Analysis by Detailed USD Guidelines** \\ \hline
**Observed Variables** & **Factor** & **Observed Variables** & **Factor** \\ \hline S4. Ensuring safety and health & 0.871 & S3.1 Simplicity & 0.837 \\ S5. Diversity and inclusion & 0.857 & S5.1 Equitable use & 0.810 \\ S3. Accessibility & 0.843 & S4.1 Error-proof design & 0.806 \\ S2. Flexibility & 0.816 & S6.2 Work sustainability & 0.795 \\ S6. Sustainability & 0.808 & S1.2 Appropriate size and space & 0.769 \\ S1. Physical support & 0.782 & S4.2 Safety and health assurance & 0.748 \\  & & S2.2 Flexible working & 0.740 \\  & & S5.2 Fairness of design policy & 0.740 \\  & & S3.2 Perceptibility & 0.689 \\  & & S6.1 Socio-ethical sustainability & 0.682 \\  & & S1.1 Low physical effort & 0.677 \\  & & S2.1 Flexible design & 0.661 \\ Explained total variance = 68.9\% & & Explained total variance = 56.0\% \\ Kaiser–Meyer–Olkin test = 0.903 & Kaiser–Meyer–Olkin test = 0.922 \\ Bartlett test \(\chi^{2}\) = 593.4, \(p\) \(<\) 0.001 & Bartlett test \(\chi^{2}\) = 1167.0, \(p\) \(<\) 0.001 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Results of factor analysis on USD guidelines.  
In Table 6, the USD guideline with the highest correlation coefficient for the mean of UD is accessibility (0.876), followed by physical support (0.843), and ensuring safety and health (0.812). On the other hand, sustainability, a concept that was absent from the UD guidelines, showed a low correlation coefficient with UD (0.693). It represents that UD guidelines are less explanatory in sustainability.  
Table 7 shows the results of the regression analysis of USD guidelines on the mean of UD. The stepwise regression equation predicting UD's mean using four variables of physical support, flexibility, accessibility, and safety and health was high explanatory power (\(R^{2}\) = 0.952). The explanatory power (\(R^{2}\) = 0.959) was also high for the five variables of physical support, flexibility, accessibility, safety and health, and inclusion. That is, USD guidelines fully explain the UD concept. Additionally, Table 7 shows that the UD was primarily influenced by accessibility, followed by flexibility.