\documentclass{article}
\begin{document}
\begin{table}
\small
\centering
\begin{tabular}{c|cc}
Source & Variation up (Stat. up) \% & Variation down (Stat. down) \% \\ \hline 
muR\_muF-Diboson\_SR2L & 11.8638 & -14.8775 \\ 
muR\_muF-Diboson\_tW2L\_CRWZ & 15.4204 & -19.0691 \\ 
muR\_muF-Diboson\_tW2L\_CRttZ & 18.976 & -25.1931 \\ 
muR\_muF-Diboson\_tW2L\_CRtt & 15.0349 & -18.5555 \\ 
muR\_muF-Diboson\_tW2L\_VRtt & 12.6552 & -14.2993 \\ 
muR\_muF-Diboson\_tW2L\_VR3L & 16.9355 & -21.5878 \\ 
\end{tabular}
\end{table}
\end{document}
