\begin{table}[]
\centering
\rowcolors{2}{lightgray!40}{}
\caption{}
\begin{tabular}{c c c c}\rowcolor{lightgray} 
Parameter & PopED & NONMEM & Pumas \\ 
$\mu_{Cl}$ & 2.5 & 2.5 & 2.5 \\ 
$\mu_{V}$ & 3.6 & 3.6 & 3.6 \\ 
$\beta_{Cl, CLCR}$ & 7 & 7 & 7 \\ 
$\beta_{V, Weight}$ & 6.8 & 6.8 & 6.8 \\ 
$\beta_{V, Sex}$ & 13 & 13 & 13 \\ 
$\omega^2_{Cl}$ & 19.1 & 19.1 & 19.1 \\ 
$\omega^2_{V}$ & 15.5 & 15.5 & 15.5 \\ 
$a^2$ & 6.4 & 6.4 & 6.4 \\ 
$b^2$ & 13.2 & 13.2 & 13.2 \\ 
\end{tabular} 
 label{tab:} 
 \end{table}