Frequencies for first 10,000 rows of chestxry variable in nhamcsed2004 dataset :

chest x-ray |      Freq.     Percent        Cum.
------------+-----------------------------------
         no |      8,121       81.21       81.21
        yes |      1,879       18.79      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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