Frequencies for first 10,000 rows of seen72 variable in nhamcsed2010 dataset :

 Seen in ED |
 within the |
    last 72 |
      hours |      Freq.     Percent        Cum.
------------+-----------------------------------
      blank |         85        0.85        0.85
    unknown |      1,712       17.12       17.97
        yes |        379        3.79       21.76
         no |      7,824       78.24      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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