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

  CT scan - |
      chest |      Freq.     Percent        Cum.
------------+-----------------------------------
         No |      9,834       98.34       98.34
        Yes |        166        1.66      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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