\begin{table}%t3                              
\caption{\label{tbl-3}Correlations and their significance from Kendall-$\tau$ statistics (K-$\tau$) and from Partial Kendall-$\tau$.}
%\centering
\par
\begin{tabular}{lccc}                           
\hline\hline\noalign{\smallskip}                
Correlation  & K-$\tau$    &  Controlling variable   &   Partial K-$\tau$\\
 & ($\sigma$) &  & ($\sigma$) \\                
\hline
  \multicolumn{4}{c}{Total} \\
   $\alphaox-\lo$ & 17  & $\z$   & 21 \\        
   $\alphaox-\lx$ & 1.2  & $\z$  & 1.5 \\    
   $\alphaox-\z$   & 7  & $\lo$ & ${<}0.1$ \\[2pt]   
\hline
  \multicolumn{4}{c}{Spectro-$z$} \\
   $\alphaox-\lo$  & 12  & $\z$  & 14 \\        
   $\alphaox-\lx$  & 0.2  & $\z$  & 2.3 \\    
   $\alphaox-\z$   & 5  & $\lo$ & ${<}0.1$ \\[2pt]   
\hline
  \multicolumn{4}{c}{Photo-$z$} \\
   $\alphaox-\lo$  & 10  & $\z$  & 12 \\        
   $\alphaox-\lx$  & 0.2  & $\z$  & 3 \\    
   $\alphaox-\z$   & 5  & $\lo$ & 0.7 \\[2pt]   
\hline
\end{tabular}                                   
\end{table}