Frequencies for first 10,000 rows of endoint variable in nhamcsed1998 dataset :

endotrachea |
          l |
 intubation |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,955       99.55       99.55
          1 |         45        0.45      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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