\begin{table}%t8
\caption{The variability parameters of B~2005+403 and the secondary calibrators
at 1.67~GHz ({\it top}) and 4.85~GHz ({\it bottom}).  Column~2 shows the mean flux density in~Jy, Col.~3 its standard deviation, Col.~4 the modulation index, Col.~5 the noise-bias corrected variability amplitude and Col.~6 the reduced~$\chi^2$.}\label{tab:m_y}
%\centering
\par
\begin{tabular}{cccccc}
\hline \hline
Source name & $\langle S\rangle {\rm ~(Jy)}$ &  $\sigma$  & ${m (\%)}$ & ${Y (\%)}$ & ${\rm red.} \chi^2$ \\ 
\hline
\multicolumn{6}{c}{$\lambda=18$~cm, $m_0=0.25$\%} \\
\hline
B~2005+403 & 2.430 & 0.024 & 1.01 & 2.93 & 5.593 \\
NGC~7027 & 1.906 & 0.004 & 0.19 & 0 & 0.197 \\
B~2021+614 & 2.193 & 0.006 & 0.25 & 0 & 0.365 \\
\hline
\multicolumn{6}{c}{$\lambda=6$~cm, $m_0=0.20$\%}\\
\hline 
B~2005+403 & 2.905 & 0.013 & 0.45 & 1.18 & 3.107 \\
NGC~7027 & 5.489 & 0.011 & 0.20 & 0 & 0.621 \\
\hline
\end{tabular}
\end{table}