Frequencies for first 10,000 rows of xray variable in nhamcsed2013 dataset :

      X-ray |      Freq.     Percent        Cum.
------------+-----------------------------------
         No |      6,913       69.13       69.13
        Yes |      3,087       30.87      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 7 Nov 2016