Frequencies for first 10,000 rows of prov1600 variable in pos1994 dataset :

    patient |
   dialysis |
   training |
       cert |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      9,780       97.80       97.80
          A |        183        1.83       99.63
          B |         34        0.34       99.97
          E |          3        0.03      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 17 May 2017