Frequencies for first 10,000 rows of incervix variable in natlterr2001 dataset :

Incompetent |
     cervix |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |         61        0.61        0.61
          2 |      9,916       99.16       99.77
          8 |         20        0.20       99.97
          9 |          3        0.03      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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