Frequencies for first 10,000 rows of pregtest variable in namcs1998 dataset :

  pregnancy |
       test |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,945       99.45       99.45
          1 |         55        0.55      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 28 Mar 2016