# CREBAS: Computer-Based REBA Evaluation System for Wood Manufacturers Using MediaPipe
## 4 Experiments and Results
### Comparison of Evaluation Results  
REBA evaluation by experts shows differences depending on the proficiency of the evaluator. In addition, it takes about 20 min to explain the REBA evaluation method and the evaluation video to the subject, and about 10 to 15 min to fill out the evaluation table. On the other hand, in the CREBA evaluation, the average time was measured by performing the evaluation 100 times for each of the seven postures, and the results are shown in Table 17.  
To verify the accuracy of the method proposed in this study, the system implemented in the selected working posture and the evaluation results of the evaluator were compared. Table 18 shows the average scores of three evaluators for six types of work postures (cutting machine, circular saw, drilling machine, saw, chisel, and planer), and Table 19 is the evaluation scores using MediaPipe. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Type** & **Data Size** & **Minimum** & **Maximum** & **Average** \\ \hline Cutter & 6.51 & 1 & 1 & 2.6 \\ Circular saw & 4.98 & 1 & 1 & 2 \\ Drilling machine & 5.11 & 1.3 & 1 & 1.3 \\ Saw & 6.76 & 0.3 & 0 & 0 \\ Chisel & 6.16 & 1.6 & 1 & 4 \\ Planer & 4.93 & 1 & 2.6 & 1 \\ Heavy load & 8.68 & 1.3 & 1.3 & 1.3 \\ \hline \hline \end{tabular}
\end{table} 
Table 17: Evaluation time required for each posture of CREBA. Figure 34: Evaluation of the posture for heavy load work. Overall, the comparison of the cutting machine working posture scores (Figure 35) showed similar results between the evaluation scores of the ergonomic expert and the evaluation scores of the proposed system. As for the scores for each joint, the MediaPipe scores were lower in all parts except the neck, and the part showing the biggest difference was the trunk, with an error of 1.3 points. The REBA scores were 4.5 points and 6.7 points, respectively, indicating the same action level (Level 2). The comparison of the circular saw working posture scores (Figure 36) showed similar results overall. The scores were the same for the trunk and upper arms, and the MediaPipe scores were lower in other parts except the neck. The part showing the biggest difference was the neck, with an error of one point. The REBA scores were three points and four points, respectively, indicating the action level of Level 2 and Level 3. As for the comparison of drilling machine working posture scores (Figure 37), the scores for each joint were the same for the trunk, legs, and wrist, and in other parts except for the neck and lower arms, where the MediaPipe scores were lower. The part showing the biggest difference was the upper arms, with an error of 1.5 points. The REBA scores were 3.5 points and 4 points, indicating the same action level (Level 2). \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Group** & **Body Part** & **Cutter** & \begin{tabular}{c} **Circular** \\ **Aw** \\ \end{tabular} & \
\begin{tabular}{c} **Drilling** \\ **Machine** \\ \end{tabular} & **Saw** & **Chisel** & **Planer** &
\begin{tabular}{c} **Heavy** \\ **Load** \\ \end{tabular} \\ \hline \multirow{4}{*}{A} & Waist & 2.3 & 1 & 1 & 2.6 & 1.6 & 2.3 & 3 \\  & Neck & 1.3 & 1 & 1 & 2 & 2 & 1.6 & 3.6 \\  & Legs & 2.3 & 1.3 & 1 & 1.3 & 1 & 1.3 & 2.3 \\  & Weight & 0 & 0.3 & 0 & 0 & 1 & 1 & 2 \\  & Score A & 4 & 1.6 & 1 & 4 & 3.3 & 3.6 & 7.3 \\  & Upper Arms & 2 & 1 & 2.6 & 1 & 0.6 & 2.6 & 3 \\  & Lower Arms & 1.6 & 1.3 & 1.3 & 1.3 & 1 & 1.6 & 1 \\  & Twist & 2 & 1 & 1 & 1.3 & 1 & 1 & 1 \\  & Handle & 1.3 & 1 & 1 & 1.3 & 0.6 & 1.3 & 3 \\ B & Score B (Left) & 4 & 2 & 3.6 & 0.6 & 1.6 & 4 & 3 \\  & Upper Arms & 1.6 & 3 & 3.3 & 1 & 1.6 & 2.3 & 3 \\  & Lower Arms & 1.6 & 1.6 & 1.3 & 1 & 1.6 & 1.6 & 1 \\  & Twist & 2 & 1.6 & 1.3 & 1 & 1 & 1 & 1 \\  & Handle & 0.6 & 0 & 0 & 0 & 0.6 & 1 & 3 \\  & Score B (Right) & 2.3 & 4 & 3.6 & 1 & 2 & 3.3 & 3 \\ REBA & Left & 6.6 & 3.6 & 3.6 & 5.3 & 5 & 7 & 13 \\ Score & Right & 5.6 & 4.3 & 4 & 5 & 5 & 6.6 & 13 \\ \hline \hline \end{tabular}
\end{table} 
Table 18: REBA evaluation results by experts (average).