\begin{table}%T3 
%\fontsize{8}{10pt}\selectfont
%\tabcolsep 0.50truecm 
\caption{Computed $R_V$ values by using different methods.}
\label{tab3}
%\centering
\par
\begin{tabular}{ll} 
\hline \hline 
Method                 & Obtained $R_V$ value \\
\hline
{\it Variable Extinction} & 3.4 $\pm$ 0.2 \\
{\it Excesses Relation}   & 4.2 $\pm$ 0.1 \\
{\it Color Difference}    & 4.0 $\pm$ 0.4 ($s.d.$) \\
\hline
\end{tabular}
\end{table}