Frequencies for first 10,000 rows of endoint variable in nhamcsed2007 dataset :

endotrachea |
          l |
 intubation |      Freq.     Percent        Cum.
------------+-----------------------------------
         no |      9,986       99.86       99.86
        yes |         14        0.14      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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