Frequencies for first 10,000 rows of pregtest variable in nhamcsed1998 dataset :

  pregnancy |
       test |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,655       96.55       96.55
          1 |        345        3.45      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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