Frequencies for first 10,000 rows of seen72 variable in nhamcsed2003 dataset :

 seen in ed |
    last 72 |
     hours? |      Freq.     Percent        Cum.
------------+-----------------------------------
      blank |        172        1.72        1.72
        yes |        293        2.93        4.65
         no |      9,029       90.29       94.94
    unknown |        506        5.06      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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