## 4 Results and Discussion
### Relationship between the Subjective Evaluation Value and Physiological Indices
#### 4.2.3 Calculation of the Evaluation Index Using Multiple Regression Analysis
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{4}{c}{**Model Summary**} \\ \hline \(R\) & 0.8657 & & Std. Error & 0.7358 \\ \(R^{2}\) & 0.7495 & & data \(N\) & 57 \\ Adjusted \(R^{2}\) & 0.7249 & & & \\ \hline
**Index** & **Coefficient** & **Std.Error** & **t** & \(p\)-value** \\ \hline Intercept & \(-3.3123\) & 0.4959 & \(-4.6631\) & \(2.28\times 10^{-5}\) \\ T7\_High-alpha & 0.1338 & 0.0201 & 6.6478 & \(1.96\times 10^{-8}\) \\ F7\_Beta/Alpha & 2.5196 & 0.3073 & 8.1996 & \(7.09\times 10^{-11}\) \\ F3\_Beta & 0.0878 & 0.0245 & 3.5817 & 0.0008 \\ F7\_Low beta & \(-0.2684\) & 0.0481 & \(-5.5791\) & \(9.29\times 10^{-7}\) \\ Fp1\_Alpha & 0.2708 & 0.0315 & 8.5969 & \(1.72\times 10^{-11}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Result of multiple regression 1 (\(Yd\)). We defined \(Yc\) as the index of thermal comfort. To confirm the possibility that \(Yc\) can evaluate thermal comfort even when there were changes in the drowsiness level, we calculated \(Yc\) from the data of nine subjects, excluding the data of participant \(D\) whose thermal comfort vote and drowsiness level vote changed slightly. We thus confirmed the relationship between \(Yc\) and the value of thermal comfort. As a result, the correlation coefficient (\(R\)) was calculated to be 0.728, and there was a significant correlation between \(Yc\) and the value of thermal comfort (\(p<0.01\)). Therefore, this result suggests that \(Yc\) can be used to evaluate thermal comfort even when there are changes in the drowsiness level. Table 1 shows the result of the multiple regression 1 (\(Yd\)), and Table 2 shows the result of the multiple regression 2 (\(Yc\)). Figure 9 shows the relationship between the drowsiness level vote and \(Yd\)(a), and the relationship between the comfort sensation and \(Yc\) (b)  
(c) Review of Continuous Evaluation using \(Yd\) and \(Yc\)  
As mentioned in Section 2.2, indices that can continuously evaluate the drowsiness level and thermal comfort of occupants are needed to clarify the design requirements related to thermal factors that can improve these states of the occupants. Therefore, we conducted a time-series analysis with \(Yd\) and \(Yc\) to confirm the possibility that \(Yd\) and \(Yc\) can continuously evaluate arousal levels and thermal comfort. We calculated the time series of \(Yd\) using data from subject C, who seemed to be drowsy frequently throughout the experiment, and compared these data with those of the drowsiness level, which was recorded at intervals of 10 s by analyzing the facial expressions of the subject based on [PERSON]'s method [20]. The time series analyses of the normalized \(Yd\) and the drowsiness level of subject C are shown in Figure 9(a),b. The figures clearly show the trend of changes in both indicators. It can be seen that \(Yd\) and values of the drowsiness level show a similar trend. For example, the red circles in Figure 9(a),b indicate that values of the drowsiness level and the normalized \(Yd\) are higher than 3 (significantly drowsy) and 0, respectively, at the same time. Furthermore, it can be seen from Figure 11 \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{4}{c}{**Model Summary**} \\ \hline \(R\) & 0.7267 & & Std. Error & 0.6859 \\ \(R^{2}\) & 0.5276 & & data \(N\) & 98 \\ Adjusted \(R^{2}\) & 0.5125 & & & \\ \hline
**Index** & **Coefficient** & **Std.Error** & **t** & \(p\)-value** \\ \hline Intercept & \(-23.3721\) & 2.5461 & \(-9.1795\) & \(1.02\times 10^{-14}\) \\ MST & 0.6967 & 0.0765 & 9.1119 & \(1.42\times 10^{-14}\) \\ C4\_Alpha/HB & 0.1718 & 0.0586 & 2.9295 & 0.0043 \\ P4\_Alpha/HB & \(-0.1418\) & 0.0296 & \(-4.7885\) & \(6.25\times 10^{-6}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Result of multiple regression 2 (\(Yc\)). Figure 9: The relationship between the drowsiness level and \(Yd\) (a), the comfort sensation and \(Yc\) (b). that there is a similar trend between \(Yc\) and the value of the comfort sensation vote.