Frequencies for first 10,000 rows of seen72 variable in nhamcsed2005 dataset :

 seen in ed |
    last 72 |
     hours? |      Freq.     Percent        Cum.
------------+-----------------------------------
      blank |        234        2.34        2.34
        yes |        405        4.05        6.39
         no |      8,480       84.80       91.19
    unknown |        881        8.81      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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