Frequencies for first 10,000 rows of arrems variable in nhamcsed2014 dataset :

 Arrival by |
  ambulance |      Freq.     Percent        Cum.
------------+-----------------------------------
      Blank |         74        0.74        0.74
    Unknown |        215        2.15        2.89
        Yes |      1,623       16.23       19.12
         No |      8,088       80.88      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 11 Apr 2017