Frequencies for first 10,000 rows of pregtest variable in namcs2009 dataset :

  pregnancy |
       test |      Freq.     Percent        Cum.
------------+-----------------------------------
         no |      9,940       99.40       99.40
        yes |         60        0.60      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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