begin{table}centering
begin{adjustbox}{width=0.45textwidth}

begin{tabular}{@{}rrrc|rrr|cr|@{}}
hline  \ [-4ex]
& multicolumn{3}{c}{textbf{Mix Rate}} & multicolumn{3}{c}{textbf{Mutation factor}}  & multicolumn{2}{c}{textbf{Crossover probability}} \

textbf{Dimensions} & $Mean$ & $Std$ && $Mean$ & $Std$  && $Mean$ & $Std$  \ midrule[0.5pt]

multicolumn{1}{l}{textbf{30}}          & 0.550 & 0.091  && 0.519 & 0.089 && 0.599 &0.133  \

multicolumn{1}{l}{textbf{50}}          & 0.549 & 0.076  && 0.521 & 0.094 && 0.565 &0.125  \

multicolumn{1}{l} {textbf{100}}        & 0.609 & 0.085  && 0.529 & 0.093 && 0.504 &0.135  \

bottomrule

end{tabular} end{adjustbox}

 end{table}