## 5 Results and Discussion
### Evaluation Method 2: SUS Evaluation Results  
An SUS score above 68 is considered above average, and a score below 68 is considered below average; thus, 68 is the average score, making it the 50 th percentile [55]. An SUS score greater than 80 is considered excellent, while a score below 51 is considered an awful design in terms of efficiency, effectiveness, and overall ease of use. Once the 20 participants filled out the SUS survey for each watch, we calculated the mean for each watch regarding that item number (#), as shown in Table 10. GW5 obtained the highest SUS score of 87.375 among all four watches, and was considered as possessing excellent usability. The battery life of these devices is one of the most significant obstacles to their acceptance and usability in consumer markets [66]. With a battery life of up to 50 h, the GW5 is the most useful in daily life, even though it is almost identical to GW4. In addition to improving battery life, the GW5 has some features that make it more appealing, such as an aluminum metal frame with a sapphire crystal display. However, GW5 is much more expensive than GW4. Moreover, the SUS score in Table 7 shows Fitbit Versa 2 has a greater usability score than Fitbit Charge 5. In the Samsung Galaxy range, the Galaxy Watch 5  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Rating** & \begin{tabular}{c} **Samsung Galaxy Watch 4,** \\ **Galaxy Wearable (Samsung** \\ **Gear) App** \\ \end{tabular}  & \begin{tabular}{c} **Samsung Galaxy Watch 5,** \\ **Galaxy Wearable (Samsung** \\ **Gear) App** \\ \end{tabular}  & \ \begin{tabular}{c} **Fitbit Charge 5, Fitbit** \\ **Application** \\ \end{tabular}  & \begin{tabular}{c} **Fitbit Versa 2, Fitbit** \\ **Application** \\ \end{tabular}  \\ \hline
\begin{tabular}{c}  
is better. From these results, we also analyzed that the latest launch of the GW5 had a higher usability value than other Samsung watches (GW4). However, in the Fitbit series, Fitbit Versa 2 was more efficient than the Fitbit Charge 5. Galaxy has higher values in odd questions, which indicates that the users mostly agree that this system is easy to use and efficient, and lower values in even questions indicating that they did not find the system unnecessarily complex and inefficient, as compared to Fitbit. From these evaluation results, we concluded that the customized heuristics and SUS both favored Galaxy Watch 5 because the evaluators identified fewer usability issues, and there were more positive comments among all four watches in terms of usability. Hence, this also demonstrated that the customized heuristics validated the heuristics for the usability evaluation of watches. In this work, we overcame the limitations of previous research with a combination of different evaluation methods and the customization of 11 heuristics for usability evaluation. We performed a comparative analysis of our findings with the previous research to find if we have generalized values with other studies. The Galaxy Watch 4's haptic bezel was identified as not being very smooth, which sometimes made navigation difficult. As a result, the user lost control and freedom, and the system became intolerable. The findings were similar to those found in other studies [67], where users found it difficult to navigate between pages when applications lacked backward and forward navigation buttons. As a result, this aspect of the design made it difficult to navigate a smartwatch. Fitbit Versa 2 does not pair automatically after resetting, thus violating the heuristic of ease of use. In addition, Fitbit Charge 5 does not support voice assistants because it does not have a microphone and speaker, making alarm settings difficult and violating the heuristic of ease of use. In a previous study [68], it was shown that ease of use in the system improves the quality experience of the user with that system. The results of the SUS survey for smartwatches showed that the users found them easy to learn and use, resulting in improved performance.