Frequencies for first 10,000 rows of seen72 variable in nhamcsed2011 dataset :

    Seen in |
    this ED |
 within the |
    last 72 |
      hours |      Freq.     Percent        Cum.
------------+-----------------------------------
      Blank |        106        1.06        1.06
    Unknown |      1,193       11.93       12.99
        Yes |        435        4.35       17.34
         No |      8,266       82.66      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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