## 5 Results and Discussion
### Pearson Correlation Coefficient and p-Value
The Pearson correlation coefficient can only measure the strength of linear relationships and may not capture the strength or form of nonlinear relationships. Therefore, this should be considered when analyzing data. Additionally, it is important to remember that correlation between two variables does not imply causation. In the Pearson correlation coefficient, the '\(p\)-value' is an indicator used to determine whether the calculated correlation coefficient is statistically significant. The \(p\)-value represents the probability of observing the calculated correlation coefficient or a more extreme value under the null hypothesis, which assumes there is no correlation between the variables. Typically, if the \(p\)-value is less than or equal to 0.05 (5%), the result is considered statistically significant. This implies that the null hypothesis can be rejected, and it can be interpreted that there is a statistically significant linear relationship between the two variables. Conversely, if the \(p\)-value is greater than 0.05, there is insufficient evidence to reject the null hypothesis, making it difficult to assert that there is a significant linear relationship between the variables. We conducted 18 questions based on a 7-point Likert scale, and as can be seen in Table 2, the 18 questions were listed vertically. On the horizontal header, only numbers were sequentially entered in correspondence to the first question on the vertical side. Regarding the impact of onboard noise on sleep, stress, and work performance, the correlation coefficient between onboard noise and sleep difficulty was the highest at 0.615, with a significant \(p\)-value of 0. The correlation between the question on the length of time it takes to fall asleep while onboard and the difficulty of sleeping due to onboard noise at night compared to daytime had a high correlation coefficient of 0.735 and a significant \(p\)-value of 0. The questions about frequently waking up during sleep and the difficulty of falling back asleep showed high correlation coefficients of 0.777 and 0.747, respectively, with significant \(p\)-values of 0. The question about the inability to get deep sleep due to noise had the highest correlation coefficient of 0.764 at night compared to daytime, with a significant \(p\)-value of 0. The question about the problems caused by sleep disorders had the highest correlation with the concern about not being able to sleep well while onboard at 0.698, with a significant \(p\)-value of 0. Regarding the noise inside the ship when the main engine is stopped compared to when it is running, the difficulty of sleeping at night had the highest correlation coefficients of 0.793 and 0.806, respectively, with significant \(p\)-values of 0. The question about not getting enough sleep while onboard had the highest correlation with the impact of inadequate sleep on daily activities at 0.664, with a significant \(p\)-value of 0. The continuous feeling of drowsiness during work hours had the highest correlation with the impact of inadequate sleep on daily activities at 0.661, with a significant \(p\)-value of 0. The question about the inability to get deep sleep due to onboard noise during sleep had a high correlation coefficient of 0.78 at night compared to daytime, with a significant \(p\)-value of 0.