

\begin{longtable}{|r|r|r|r|}\hline
   \multicolumn{4}{|c|}{Extreme Observations}\\\hline
   \multicolumn{2}{|c|}{Lowest} &    \multicolumn{2}{|c|}{Highest}\\\hline
   Value &    Obs &    Value &    Obs\\\hline
\endhead
   3.3 &    12 &    5.5 &    14\\\hline
   4.5 &    13 &    6.4 &    18\\\hline
   5.0 &    15 &    7.1 &    20\\\hline
   5.3 &    19 &    7.6 &    16\\\hline
   5.4 &    11 &    7.6 &    17\\\hline
\end{longtable}

