Frequencies for first 10,000 rows of endoint variable in nhamcsed2013 dataset :

Endotrachea |
          l |
 intubation |      Freq.     Percent        Cum.
------------+-----------------------------------
         No |      9,980       99.80       99.80
        Yes |         20        0.20      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 7 Nov 2016