data one;
  input patient before after;
  cards;
1   30 120
2   45 240
3  180 480
4   15 150
5  200 480
6   20 270
7   15 300
8   10 180
9   20 300
10  20 240
11  60 480
12  60 300
13 120 480
;

data one; set one;
  ratio=after/before;
  Y=log(ratio);
run;

proc univariate plot;
  var ratio Y;
run;

proc means data=one mean std stderr clm alpha=0.05;
  var ratio Y;
run;