\begin{table}%t6
  \caption{\label{simulations}Results of simulations done to investigate the impact of selection 
    effects on the observed fractions of SCCs, WCCs, and NCCs.} 
  \small
  %\centering
\par
  \begin{tabular}{cccc}
    \hline\hline
    Case                    & Category & Input        & Output     \\       
                               &                & fractions  &  fractions \\ 
    \hline                                                                                        
    Same slope         & SCC~        & 0.34                  & 0.437~$\pm$~0.043   \\
                               & WCC~       & 0.36                  & 0.281~$\pm$~0.041   \\
                               & NCC~       & 0.30                  & 0.281~$\pm$~0.044   \\ 
    \hline
    Different slopes  & SCC~        & 0.310                & 0.445~$\pm$~0.041   \\
                               & WCC~       & 0.335                 & 0.275~$\pm$~0.038  \\
                               & NCC~       & 0.355                 & 0.280~$\pm$~0.041  \\
     \hline
  \end{tabular}\vspace*{-3mm}
\end{table}