Frequencies for first 10,000 rows of seen72 variable in nhamcsed2004 dataset :

 seen in ed |
    last 72 |
     hours? |      Freq.     Percent        Cum.
------------+-----------------------------------
      blank |        330        3.30        3.30
        yes |        282        2.82        6.12
         no |      8,962       89.62       95.74
    unknown |        426        4.26      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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