The TTEST Procedure

Overview: TTEST Procedure

The TTEST procedure performs $\text{[math]}$ tests and computes confidence limits for one sample, paired observations, two independent samples, and the AB/BA crossover design. Two-sided, TOST (two one-sided test) equivalence, and upper and lower one-sided hypotheses are supported for means, mean differences, and mean ratios for either normal or lognormal data.

Table 92.1 summarizes the designs, analysis criteria, hypotheses, and distributional assumptions supported in the TTEST procedure, along with the syntax used to specify them.

Table 92.1 Features Supported in the TTEST Procedure
Feature	Syntax
Design
One-sample	VAR statement
Paired	PAIRED statement
Two-independent-sample	CLASS statement, VAR statement
AB/BA crossover	VAR / CROSSOVER
Analysis Criterion
Mean difference	PROC TTEST TEST=DIFF
Mean ratio	PROC TTEST TEST=RATIO
Hypothesis
Two-sided	PROC TTEST SIDES=2
Equivalence	PROC TTEST TOST ( <lower ,> upper )
Lower one-sided	PROC TTEST SIDES=L
Upper one-sided	PROC TTEST SIDES=U
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, Q-Q plots, profiles, and agreement plots.

PROC TTEST now 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.

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