Frequencies for first 10,000 rows of arrems variable in nhamcsed2015 dataset :

 Arrival by |
  ambulance |      Freq.     Percent        Cum.
------------+-----------------------------------
      Blank |        103        1.03        1.03
    Unknown |        236        2.36        3.39
        Yes |      1,756       17.56       20.95
         No |      7,905       79.05      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 20 Nov 2017