Frequencies for first 10,000 rows of seen72 variable in nhamcsed2008 dataset :

 seen in ed |
    last 72 |
     hours? |      Freq.     Percent        Cum.
------------+-----------------------------------
      blank |        135        1.35        1.35
    unknown |      1,325       13.25       14.60
        yes |        428        4.28       18.88
         no |      8,112       81.12      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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