Frequencies for first 10,000 rows of f_uob_amnio variable in natlterr2005 dataset :

Amniocentes |
       is U |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      5,476       54.76       54.76
          1 |      4,524       45.24      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 22 Dec 2015