|
Path: janda.org/c10
> Overview
of SPSS
>
Analyze
>
T-Test
|
Statistical
Package
for the
Social
Sciences
Syntax for T-TEST Command
|
T-Test
Use the T-TEST procedure to test for a
statistically significant difference in means
between two groups. The T-TEST computes a
t-value which is a standardized score, similar to a
z-score.
The t-value is calculated by dividing the difference
in means between the groups by the standard error of the
sampling difference between means. Remember that
the "standard error" of a statistic (the statistic here
is the value of the difference between the means) is just
another name for the standard deviation of the sampling
distribution for that statistic. The syntax for the most
common T-TEST command is as follows:
|
|
T-TEST
|
The "groupvar" is the name of the variable used to
create the two groups being compared. For example, "Region"
might be the variable that furnishes the groups.
(n1,n2) indicates the two values of the groups being
compared. To compare European nations with African nations
in the POLITY dataset, specify (2,6).
variable is the name of the variable to analyze for
difference of means. Suppose that you wanted to compare
European nations with African nations for the percent of
land under cultivation. The name of the variable in the
POLITY data would be landcult.
REGION seven world regions (POLITY dataset)
Valid Cum
Value Label Value Frequency Percent Percent Percent
ANGLO-AMERICAN 1 5 4.5 4.5 4.5
EUROPEAN 2 17 15.3 15.3 19.8
LATIN AMERICAN 3 23 20.7 20.7 40.5
ASIA 4 15 13.5 13.5 54.1
MIDDLE EAST 5 11 9.9 9.9 64.0
AFRICA 6 32 28.8 28.8 92.8
EASTERN EUROPE 7 8 7.2 7.2 100.0
----- ------ ------
Total 111 100.0 100.0
|
|
|
GROUPS =
groupvar
(n1,n2) /
VARIABLES =
variable
|
|
T-TEST output
|
- 2 t-test groups=
region (2,6) variables=landcult.
t-tests
for Independent Samples of REGION
seven world regions
|
|
Variable
|
Number
of Cases
|
Mean
|
SD
|
SE of Mean
|
|
|
LANDCULT % OF
LAND UNDER ACTUAL CULTIVATION
|
|
EUROPE
|
16
|
29.0000
|
17.588
|
4.397
|
|
|
AFRICA
|
31
|
11.1065
|
10.988
|
1.974
|
|
|
Mean Difference =
17.8935
Levene's Test for Equality of Variances:
F= 5.620 P=
.022
t-test for
Equality of Means 95%
|
|
Variances
|
t-value
|
df
|
2-Tail Sig.
|
SE of
Diff
|
CI for
Diff
|
|
Equal
|
4.29
|
45
|
.000
|
4.171
|
(9.493,
26.295)
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
df 2-Tail
Sig
------------------------------------------------------
. . 45 .000
Unequal . 3.71 . 21.22
.001 4.820 (7.877, 27.910)
------------------------------------------------------
|
|