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

Endotrachea |
          l |
 intubation |      Freq.     Percent        Cum.
------------+-----------------------------------
         No |      9,979       99.79       99.79
        Yes |         21        0.21      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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