Frequencies for first 10,000 rows of chestxry variable in nhamcsopd1992 dataset :

Chest x-ray |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,632       96.32       96.32
          1 |        368        3.68      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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