Frequencies for first 10,000 rows of chlamyd variable in namcs2006 dataset :

  chlamydia |
       test |      Freq.     Percent        Cum.
------------+-----------------------------------
         no |      9,960       99.60       99.60
        yes |         40        0.40      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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