# Absolute Reliability and Concurrent Validity of the Modified
## 3 Results
### Validity  
The correlation between the MGP and 2D video analysis for measuring right trunk rotation (r = 0.986) and left trunk rotation (r = 0.981) was significant (\(p\) < 0.001), with explained variances of 97.2% and 96.2%, respectively (Table 3). Therefore, there was a strong relationship between the two instruments for measuring trunk rotation. The Bland-Altman plot showed the level of agreement between the two instruments for right \begin{table}
\begin{tabular}{l c c c c c c c c} \hline \hline \multicolumn{1}{c}{\multirow{2}{*}{**Action**}} & \multicolumn{2}{c}{**Rater 1**} & \multirow{2}{*}{**SEM (\({}^{\circ}\))**} & \multirow{2}{*}{**MDC (\({}^{\circ}\))**} & \multicolumn{2}{c}{**Rater 2**} & \multirow{2}{*}{**SEM (\({}^{\circ}\))**} & \multirow{2}{*}{**MDC (\({}^{\circ}\))**} & \multirow{2}{*}{**ICC**} \\  & & **Mean \(\pm\) SD** & & & & & & **[95\% CI]** \\ \hline Right trunk rotation & 45.412 \(\pm\) 8.181 & 0.818 & 2.267 & 45.255 \(\pm\) 8.447 & 0.845 & 2.342 & 0.990 \\ (test session) & & & & & & & [0.982 0.994] \\ Left trunk rotation & 43.843 \(\pm\) 9.085 & 0.953 & 2.642 & 44.157 \(\pm\) 8.889 & 0.932 & 2.583 & 0.989 \\ (test session) & & & & & & & [0.980 0.993] \\ Right trunk rotation & 47.569 \(\pm\) 8.346 & 0.988 & 2.739 & 47.490 \(\pm\) 8.606 & 1.078 & 2.988 & 0.986 \\ (re-test session) & & & & & & & [0.982 0.998] \\ Left trunk rotation & 46.235 \(\pm\) 8.116 & 1.200 & 3.326 & 46.784 \(\pm\) 8.333 & 1.236 & 3.426 & 0.978 \\ (re-test session) & & & & & & [0.960 0.988] \\ \hline \hline \end{tabular} ICC, intra-class correlation coefficient; SEM, standard error of measurement; MDC, minimum detectable change.  
\end{table} 
Table 1: Inter-rater reliability of the MGP for left and right trunk rotations. \begin{table}
\begin{tabular}{l c c c c c c c c} \hline \hline \multicolumn{1}{c}{\multirow{2}{*}{**Action**}} & \multicolumn{2}{c}{**Measurement1**} & \multirow{2}{*}{**SEM (\({}^{\circ}\))**} & \multirow{2}{*}{**MDC**} & \multicolumn{2}{c}{**Measurement2**} & \multirow{2}{*}{**SEM (\({}^{\circ}\))**} & \multirow{2}{*}{**MDC**} & \multirow{2}{*}{**ICC**} \\  & & **(Test)** & & & & & & **Mean \(\pm\) SD** & & **[95\% CI]** \\ \hline \multirow{3}{*}{Rater 1} & Right trunk & 45.706 \(\pm\) 8.060 & 1.820 & 5.045 & 47.294 \(\pm\) 8.608 & 1.944 & 5.388 & 0.949 \\  & rotation & & & & & & [0.852 0.982] \\ \cline{1-1}  & Left trunk & 44.294 \(\pm\) 9.224 & 2.183 & 6.051 & 46.000 \(\pm\) 8.624 & 2.041 & 5.657 & 0.944 \\ \cline{1-1}  & rotation & & & & & & [0.839 0.980] \\ \cline{1-1}  & Right trunk & 45.529 \(\pm\) 8.420 & 1.806 & 5.006 & 47.235 \(\pm\) 8.884 & 1.905 & 5.280 & 0.954 \\ \cline{1-1}  & rotation & & & & & & [0.858 0.984] \\ \cline{1-1}  & left trunk & 44.412 \(\pm\) 8.832 & 2.052 & 5.688 & 46.059 \(\pm\) 8.035 & 1.867 & 5.175 & 0.946 \\ \cline{1-1}  & rotation & & & & & & [0.840 0.981] \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Intra-rater reliability of the two measurements performed by raters. transverse plane. Therefore, MGP has strong validity and reliability as an instrument for evaluating trunk rotation in the seated position. Trunk rotation was reported to have a good-to-excellent inter-rater reliability. The inter-rater coefficients of reliability of a standard 8-inch (20-centimetre) transparent plastic goniometer for measuring right and left trunk rotations in the sitting position were 0.870 (95% CI: 0.770-0.930) and 0.870 (95% CI: 0.760-0.930), respectively, indicating a good inter-rater reliability [23]. The right trunk rotation values measured by two previous raters were 54.4\({}^{\circ}\)\(\pm\) 10.5\({}^{\circ}\) and 53.4\({}^{\circ}\)\(\pm\) 11.0\({}^{\circ}\), and those of the left trunk rotation were 53.7\({}^{\circ}\)\(\pm\) 9.0\({}^{\circ}\) and 55.3\({}^{\circ}\)\(\pm\) 11.1\({}^{\circ}\)[23].