## 5 System Evaluation
### Evaluation Results  
Table 3 provides the average results of two exams, which were attempted by 40 four-year construction students before and after using the iAPR system for learning. To objectively compare the learning outcome of the learners, a paired sample T-test (called the dependent sample \(t\)-test) was developed to determine whether the mean difference between the two exams was statistically significant. The null hypothesis was that the mean difference between the two exam scores is equal, while the alternative hypothesis was that the mean difference between the two exam scores is not equal. The SPSS.20 statistics software was utilized to statistically analyze the before-exam and after-exam scores at the 5% significance level. According to Table 3, the mean value and standard deviation are 76.250 and 4.770, respectively for the before-exam, while they are 80.125 and 4.001, respectively, for the after-exam. Since the Sig. (2-tailed) value of 0.001 (see Table 4) is less than the significance level of 0.05, the null hypothesis was rejected. Because of this, it is concluded that there is a statistically significant  
Figure 5: System evaluation scheme. difference between the mean scores of the two exams. Meanwhile, the effectiveness evaluation results in Table 3 reveal that learners using the iAPR system for construction hazard investigation would have higher scores (80.125) than those who do not utilize the proposed platform for learning (76.250). Therefore, it proves that the proposed iAPR system can assist learners in improving hazard investigation knowledge and skill. Figure 6 depicts the results of iAPR usability evaluation, focusing on the six aforementioned criteria. The interviews and questionnaires related to the criteria for usability evaluation were conducted with all participants including the ten educators, ten construction managers, and 40 learners right after they experienced the iAPR prototype. For the first question \"your sense of being in the construction site\", which was adopted from [56], all the participants totally agreed that they had a good sense of being in a real construction workplace. Moreover, the users stated that the iAPR design is intuitive so that they could easily investigate and inspect the potential hazards by using mouses (for PCs, laptops) or their own fingers (for smart devices). The functions and tools designed in the iAPR prototype are user-friendly and similar to popular applications in various operating environments such as PCs and laptops as well as smart devices (e.g., ipad, tablets); therefore, it is easy for users to interact with the virtual environment. Regarding real-world visibility, the learners emphasized the advantage of the 360 VP technology, which could present the virtual jobsite more realistically than other 3D-VR technologies. They also pointed out that the support of 3D object anatomization function in the iAPR is very necessary to assist learners in proposing prevention methods, which are very important for hazard elimination. Finally, the participants agreed that the iAPR motivates and engages them in learning construction hazard investigation and inspection. \begin{table}
\begin{tabular}{l l l l l l l l l} \hline \hline  & \multicolumn{6}{c}{**Paired Differences**} \\ \hline \multirow{2}{*}{**Mean**} & \multirow{2}{*}{\begin{tabular}{c} **Std.** \\ **Deviation** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Std. Error** \\ **Mean** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **95\% Confidence Interval** \\ **of the Difference** \\ \end{tabular} } & \multirow{2}{*}{\
\begin{tabular}{c} **t** \\ **df** \\ \end{tabular} } & \multirow{2}{*}{
\begin{tabular}{c} **df** \\ **Sig. (2-Tailed)** \\ \end{tabular} } \\ \cline{5-8}  & & & & **Lower** & & **Upper** & & \\ \hline Pair: & & & & & & & \\ Before-After & \(-3.87500\) & \(5.48746\) & \(0.86764\) & \(-5.62997\) & \(-2.12003\) & \(-4.466\) & \(39\) & \(0.000\) \\ exams & & & & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Paired Samples Test.