/* Entering the pollution data */

DATA pollution;
INFILE cards missover;
INPUT location $ @;
 DO until (pollut = .);
 INPUT pollut @;
 IF pollut ne . then OUTPUT;
 END;
lines;
upstrm 24.5 29.7 20.4 28.5 25.3 21.8 20.2 21.0 21.9 22.2 .
downstrm 32.8 30.4 32.3 26.4 27.8 26.9 29.0 31.5 31.2 26.7 25.6 25.1 32.8 34.3 35.4 .
run;

/* Sorting and getting separate box plots for the data */
PROC SORT;
BY location;
run;

PROC UNIVARIATE PLOT;
VAR pollut;
BY location;
run;

/* The two-sample t-test is performed by PROC TTEST */
/* A CI for mu_1 - mu_2 (here, 95%) is also printed */
PROC TTEST;
CLASS location;
VAR pollut;
run;

/* A different confidence level (say, 99%) for the CI may be specified: */
PROC TTEST ALPHA=0.01;
CLASS location;
VAR pollut;
run;