Frequencies for first 10,000 rows of prov1600 variable in pos1995 dataset :

    patient |
   dialysis |
   training |
       cert |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      9,752       97.52       97.52
          A |        210        2.10       99.62
          B |         35        0.35       99.97
          E |          3        0.03      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 26 Jan 2016