User Guide

362
Chapter 20
Statistics. For each variable: mean, sample size, standard deviation, and standard
error of the mean. For each pair of variables: correlation, average difference in means,
t test, and c
onfidence interval for mean difference (you can specify the confidence
level). Standard deviation and standard error of the mean difference.
Data. For each paired test, specify two quantitative variables (interval- or ratio-level of
measuremen
t). For a matched-pairs or case-control study, the response for each test
subject and its matched control subject must be in the same case in the data file.
Assumptions. Observations for each pair should be made under the same conditions.
The mean di
fferences should be normally distributed. Variances of each variable
can be equal or unequal.
Figure 20-
6
Paired-Sa
mples T Test output
116.40 10 13.62 4.31
142.50 10 17.04 5.39
After
treatment
Before
treatment
Pair 1
Mean N
Std.
Deviation
Std. Error
Mean
Paired Samples Statistics
-26.10 19.59 6.19 -40.11 -12.09 -4.214 9 .002
After
treatment -
Before
treatment
Pair 1
Mean
Std.
Deviation
Std. Error
Mean
Lower Upper
95% Confidence Interval
of the Difference
Paired Differences
t df
Significance
(2-tailed)
Paired Samples Test
To Obtain a Paired-Samples T Test
E From the menus choose:
Analyze
Compare Means
Paired-Samples T Test...