## 4 Result
### Predictive Modelling of HRV and Stress
#### 4.3.2 Ordinal Logistic Regression for the PSS
The model's predicted log-odds for low and moderate stress states based on all predictors are shown in Equations (1) and (2), respectively. \[Ln[p(y\leq 1)]=2.2372-0.3518X_{1}+0.0211X_{2}+0.0280X_{3}+0.6762X_{4}+1.1370X_{5}-0.4257X_{6}-0.6041X_{7} \tag{1}\] \[-0.4143X_{8}+0.6836X_{9}-0.0088X_{10}+0.0051X_{11}-0.0023X_{12}\] \[Ln[p(y\leq 2)]=3.9664-0.3518X_{1}+0.0211X_{2}+0.0280X_{3}+0.6762X _{4}+1.1370X_{5}-0.4257X_{6}-0.6041X_{7}\] (2) \[-0.4143X_{8}+0.6836X_{9}-0.0088X_{10}+0.0051X_{11}-0.0023X_{12}\]  
Here, \(p(y\leq 1)\) presents the probability value that the perceived stress is low; \(p(y\leq 2)\) presents the probability value that the perceived stress is low and high. In Equations (1) and (2), \(Ln[p(y\leq 1)]\) and \(Ln[p(y\leq 2)]\) represent the logarithms of probability. \(X1\), \(X2\), \(X3\), \(\ldots\)\(X12\), denote age, experience, the MRR on segment 2, and the LF/HF ratios on each segments, respectively, along with mental, physical, and performance demands; \(Y\) denotes the PSS level. The model was statistically significant based on the likelihood ratio test (\(p=0.0135\)) and the parallelism test (\(p=1\)), confirming that the independent variables used in the model significantly explain variations in PSS results. The ordinal logistic regression model assesses the relationship between physiological, cognitive, and demographic factors in predicting perceived stress levels. Age (\(\beta=-0.3518\), \(p=0.027\), OR = 0.7034) is a statistically significant predictor, indicating that as age increases, the likelihood of experiencing higher stress decreases. MRR2 (\(\beta=0.0280\), \(p=0.006\), OR = 1.0284) also shows a significant positive association with stress, suggesting that individuals with higher MRR2 values have an increased probability of experiencing higher stress. Furthermore, LFHF2 (\(\beta=1.1370\), \(p=0.035\), OR = 3.1173) is a significant predictor, implying that increased LFHF2 values, which indicate greater sympathetic nervous system activity, are associated with a higher likelihood of perceived stress. Conversely, LFFH3 (\(p=0.192\)), LFFH4 (\(p=0.143\)), LFFH5 (\(p=0.451\)), and LFFH6 (\(p=0.889\)) were not statistically significant, indicating that these specific HRV-related parameters do not meaningfully contribute to stress perception in this model. Additionally, experiences (\(p=0.870\)), LFFH1 (\(p=0.244\)), MD (\(p=0.111\)), PD (\(p=0.597\)), and OP (\(p=0.679\)) were also not significant, suggesting that cognitive- and workload-related factors may not be primary determinants of perceived stress. Exploration of Effects of Mariner's License and Last Ship Experience on Subjective Stress, WL, and Physiological Stress Responses  
We further explored the relationships between subjective and physiological stress indicators with three key variables: (1) CoC; (2) last position on board; (3) type of last ship experience. Using the Kruskal-Wallis H test for non-parametric group comparisons, we analyzed whether these categorical background variables were associated with significant differences in perceived stress, workload ratings (NASA-TLX subscales), and HRV-based physiological responses (SDNN, RMSSD, MRR, LF/HF ratio) across six simulation segments. The analysis found no significant differences in PSS scores or HRV-based physiological indicators across groups stratified by last rank or last ship type. However, the CoC level showed a statistically significant effect on the NASA-TLX frustration subscale (H = 6.2421, \(p\) = 0.0125), as shown in Figure 9, while the ANT II participants exhibited higher frustration levels than ANT I. Furthermore, a multiple linear regression was conducted to evaluate whether the CoC, last position onboard, or last ship type experience could significantly predict the subjective stress (PSS), perceived workload (NASA-TLX subscales), or physiological stress responses (HRV metrics). The regression revealed that the CoC level (ANT II) was a marginally significant predictor of frustration.