Frequencies for first 10,000 rows of pregtest variable in nhamcsopd1998 dataset :

  pregnancy |
       test |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,841       98.41       98.41
          1 |        159        1.59      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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