

\begin{longtable}{|l|l|r|r|l|}\hline
   \multicolumn{5}{|c|}{Means with the same letter are not significantly different.}\\\hline
   \multicolumn{2}{|c|}{Duncan~Grouping} &    Mean &    N &    Year\\\hline
\endhead
     &    A &    5.9900 &    10 &    1968\\\hline
     &    A &      &      &     \\\hline
   B &    A &    5.7700 &    10 &    1969\\\hline
   B &      &      &      &     \\\hline
   B &      &    4.9100 &    10 &    1970\\\hline
   B &      &      &      &     \\\hline
   B &      &    4.8000 &    10 &    1971\\\hline
   B &      &      &      &     \\\hline
   B &      &    4.7200 &    10 &    1972\\\hline
\end{longtable}

