Frequencies for first 10,000 rows of xray variable in namcs2007 dataset :

      x-ray |      Freq.     Percent        Cum.
------------+-----------------------------------
         no |      9,429       94.29       94.29
        yes |        571        5.71      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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