Frequencies for first 10,000 rows of chestxry variable in nhamcsed1996 dataset :

chest x-ray |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      8,460       84.60       84.60
          1 |      1,540       15.40      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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