## 3 Results
### Step V: Perform RCA  
#### 3.5.1 Orthogonal Arrays (OAs)  
Orthogonal array (OA) was introduced as an approach utilized for the feature selection mechanism. OA incorporates the use of \"1\" and \"2\" for two-level factors, as shown in Tables 11 and 12. This is normally a two-level array where the variables are different within two levels. In this array, an optimum of eleven factors can be allocated. The twelve combinations with 2s and 1s correspond to the different variable combinations to be examined. 1s and 2s correspond to the presence (on) and absence (off) of the variable, respectively.  
In this study, eleven variables were allocated to the first 11 columns of the orthogonal array. The last column was reserved for the responses of the combinations of the five variables. In the root cause analysis (RCA), the response was the MD corresponding to the variables in the respective combination (Table 11). The MDs in terms of the physical layout are listed in Table 11. For RCA, two-level arrays are preferred to ascertain the importance of the variables when the system is \"on\" and \"off\"; see Table 12. For the first combination, all variables were included, and MD was computed for a given participant. In the second combination, variables X3, X4, X5, X6, and X7 were used, and MD was computed with these five variables for the same participant. MDs for all other combinations were computed in a similar manner.  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Combination**} & \multicolumn{8}{c}{**Variables**} \\ \cline{2-10}  & **X3** & **X4** & **X5** & **X6** & **X7** & **X9** & **X10** & **X11** \\ \hline
3 & 1 & 1 & 2 & 2 & 2 & 1 & 1 & 1 \\
4 & 1 & 2 & 1 & 2 & 2 & 1 & 2 & 2 \\
5 & 1 & 2 & 2 & 1 & 2 & 2 & 1 & 2 \\
6 & 1 & 2 & 2 & 2 & 1 & 2 & 2 & 1 \\
7 & 2 & 1 & 2 & 2 & 1 & 1 & 2 & 2 \\
8 & 2 & 1 & 2 & 1 & 2 & 2 & 2 & 1 \\
9 & 2 & 1 & 1 & 2 & 2 & 2 & 1 & 2 \\
10 & 2 & 2 & 2 & 1 & 1 & 1 & 1 & 2 \\
11 & 2 & 2 & 1 & 2 & 1 & 2 & 1 & 1 \\
12 & 2 & 2 & 1 & 1 & 2 & 1 & 2 & 1 \\ \hline \hline \end{tabular}
\end{table}
Table 11: L\({}_{12}\) (2\({}^{8}\)) OA of ACLR conditions.  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multicolumn{1}{c}{**Variables**} & \multirow{2}{*}{**Response**} & \multirow{2}{*}{**Response for RCA**} \\ \cline{2-10}  & **X3** & **X4** & **X5** & **X6** & **X7** & **X9** & **X7** & **X8** \\ \hline
1 & On & On & On & On & On & On & On & On & MD1 & D1 = \(\sqrt{\text{MD1}}\) \\
2 & On & On & On & On & On & Off & Off & Off & MD2 & D1 = \(\sqrt{\text{MD2}}\) \\
3 & On & On & Off & Off & Off & Off & On & On & MD3 & D1 = \(\sqrt{\text{MD3}}\) \\
4 & On & Off & On & Off & Off & Off & Off & Off & MD4 & D1 = \(\sqrt{\text{MD4}}\) \\
5 & On & Off & Off & On & Off & Off & On & Off & MD5 & D1 = \(\sqrt{\text{MD5}}\) \\
6 & On & Off & Off & Off & Off & On & Off & Off & MD6 & D1 = \(\sqrt{\text{MD6}}\) \\
7 & Off & On & Off & Off & Off & On & Off & Off & MD7 & D1 = \(\sqrt{\text{MD7}}\) \\
8 & Off & On & Off & On & Off & Off & Off & On & MD8 & D1 = \(\sqrt{\text{MD8}}\) \\
9 & Off & On & On & Off & Off & Off & Off & Off & MD9 & D1 = \(\sqrt{\text{MD9}}\) \\
10 & Off & Off & Off & On & On & On & On & Off & MD10 & D1 = \(\sqrt{\text{MD10}}\) \\
11 & Off & Off & On & Off & On & Off & On & On & MD11 & D1= \(\sqrt{\text{MD11}}\) \\
12 & Off & Off & On & On & Off & On & Off & On & MD12 & D1 = \(\sqrt{\text{MD12}}\) \\ \hline \hline \end{tabular}
\end{table}
Table 12: Physical layout of corresponding to L\({}_{12}\) (2\({}^{8}\)) orthogonal array with 11 variables.