Biometry (Biol 620)
1
SPSS for One-sample, Two-sample, and Paired T-tests
One-sample T-test
I. Data File Format
- need one column that contains the data for each replicate (each row). See the data file example below:
7.07
5.30
4.91 etcโฆ.
II. Analysis
(1) From the pull-down menu:
Analyze
โ
Compare Means
โ
one-sample T-test <click on this>
(2) (a) Click to highlight the dependent variable column name in the left window menu, then click on the arrow to
move it to the right window to define the DEPENDENT VARIABLE.
(b) In the โTest Valueโ window at the bottom right, type in the expected value against which you want to test
the sample mean. Then click the โOKโ button to run the analysis.
III. Result
Two-sample T-test
I. Data File Format
- need two columns; one that specifies which treatment group each data value comes from and one that contains the
data for each replicate. See the data file example below; column 1 = treatment, column 2 = data:
1 7.07
1 5.30
2 4.91
2 5.72 etcโฆ.
II. Analysis
(1) From the pull-down menu:
Analyze
โ
Compare Means
โ
independent-samples T-test <click on this>
(2) Click to highlight the dependent variable column name in the left window, then click on the arrow to move it to
the โTest Variableโ window to define the DEPENDENT VARIABLE. Then highlight the independent
variable column name in the left window, then click the arrow to move it to the โGrouping Variableโ window.
(3) Click on the โDefine Groupsโ button to reveal a window in which you type in the letters, numbers, or words
(case sensitive) that define the two treatment groups: โTest Group 1โ and โTest Group 2โ. Click the
โContinueโ button to return to the previous window. Then click the โOKโ button to run the analysis.
III. Result
Independent Samples Test
35.907 .000 -33.766 766 .000 -16.634 .4926 -17.6014 -15.6672
-34.178 691.063 .000 -16.634 .4867 -17.5899 -15.6787
Equal variances
assumed
Equal variances
not assumed
CL
FSig.
Levene's Test for
Equality of Variances
tdf Sig. (2-tailed)
Mean
Difference
Std. Error
Difference Lower Upper
95% Confidence
Interval of the
Difference
t-test for Equality of Means
One-Sample Test
4.302 767 .000 1.670 .908 2.432
CL
tdf Sig. (2-tailed)
Mean
Difference Lower Upper
95% Confidence
Interval of the
Difference
Test Value = 30
