data one;
  input year rate ssact $;
  cards;
1938  0.8    LOW  
1939  1.3    HIGH  
1940  1.4    HIGH  
1941  1.2    HIGH  
1942  1.7    LOW  
1943  1.8    LOW  
1944  1.6    LOW  
1945  1.5    LOW  
1946  1.5    LOW  
1947  2.0    LOW  
1948  2.5    HIGH  
1949  2.7    HIGH  
1950  2.9    HIGH  
1951  2.5    HIGH  
1952  3.1    HIGH  
1953  2.4    LOW  
1954  2.2    LOW  
1955  2.9    LOW  
1956  2.5    LOW  
1957  2.6    LOW  
1958  3.2    LOW  
1959  3.8    HIGH  
1960  4.2    HIGH  
1961  3.9    HIGH  
1962  3.7    HIGH  
1963  3.3    LOW  
1964  3.7    LOW  
1965  3.9    LOW  
1966  4.1    LOW  
1967  3.8    LOW  
1968  4.7    LOW  
1969  4.4    LOW  
1970  4.8    HIGH  
1971  4.8    HIGH  
1972  4.8    HIGH  
;

proc sort data=one out=one;
  by ssact;
run;

proc print;
run;

proc univariate plot;
  var rate;
  by ssact;
run;

proc ttest;
  var rate;
  class ssact;
run;

data high; set one;
  if ssact='LOW' then delete;
run;

proc print data=high;
run;

proc plot data=high;
  plot rate*year;
run;

data low; set one;
  if ssact='HIGH' then delete;
run;

proc print data=low;
run;

proc plot data=low;
  plot rate*year;
run;

proc plot data=one;
  plot rate*year=ssact;
run;