The TTEST procedure performs t tests and computes confidence limits for one sample, paired observations, two independent samples, and the AB/BA crossover design. Twosided, TOST (two onesided test) equivalence, and upper and lower onesided hypotheses are supported for means, mean differences, and mean ratios for either normal or lognormal data.
Table 99.1 summarizes the designs, analysis criteria, hypotheses, and distributional assumptions supported in the TTEST procedure, along with the syntax used to specify them.
Table 99.1: Features Supported in the TTEST Procedure
Feature 
Syntax 

Design 

Onesample 
VAR statement 
Paired 
PAIRED statement 
Twoindependentsample 

AB/BA crossover 

Analysis Criterion 

Mean difference 
PROC TTEST TEST=DIFF 
Mean ratio 
PROC TTEST TEST=RATIO 
Hypothesis 

Twosided 

Equivalence 
PROC TTEST TOST ( <lower ,> upper ) 
Lower onesided 

Upper onesided 

Distribution 

Normal 
PROC TTEST DIST=NORMAL 
Lognormal 
PROC TTEST DIST=LOGNORMAL 
FREQ and WEIGHT statements are available. Data can be input in the form of observations or, in certain cases, summary statistics. Output includes summary statistics; confidence limits for means, standard deviations, and coefficients of variation; hypothesis tests; and a variety of graphical displays, including histograms, densities, box plots, confidence intervals, QQ plots, profiles, and agreement plots.
PROC TTEST uses ODS Graphics to create graphs as part of its output. For general information about ODS Graphics, see Chapter 21: Statistical Graphics Using ODS. For specific information about the statistical graphics available with the TTEST procedure, see the PLOTS option in the PROC TTEST statement and the section ODS Graphics.