Frequencies for first 10,000 rows of endoint variable in nhamcsed1999 dataset :

endotrachea |
          l |
 intubation |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,969       99.69       99.69
          1 |         31        0.31      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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