SPSS 18
Simple Data Analysis
Sheila Dixon & Diane Skinner - September 2010
Statistical Help
Descriptives command
There are over 60 different procedures that can be
used to analyse data via the Analyze menu
1.
Select Descriptive Statistics from the Analyze
menu and Descriptives from the sub-menu.
2. Highlight the variable(s) required and click on the
arrowhead to add to the Descriptives box.
The Statistics Coach
You may not be sure which statistical procedure to
follow in which the case the Statistics coach may prove
useful.
1.
Open SPSS in Data Editor view.
2. Select the Statistics Coach from the Help menu.
You will be asked a number of non-technical questions
regarding the type of data you have and what you hope
to do. On completion you are advised on the procedure
to use.
3. Click on the Options button to generate more
statistics. Descriptive Options
Exploring Data
The best place to start is using the Frequencies (for
nominal data) and the Descriptives (for numerical
data).
Frequencies
1.
Choose Descriptive Statistics from the Analyze
menu and Frequencies from the sub-menu.
2. Highlight the variable to create the frequencies for
in the left panel and click on the arrowhead to add
it to the variable panel.
Click on the Statistics
button to add descriptives
to the output.
To add a pie
or bar chart,
or histogram
select the
chart option
3. Click OK to accept options.
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The format option
allows you to
change the order the
data is displayed in
Mean and Sum
are displayed by default.
Dispersion
measures the spread of the
data, standard deviation,
range etc.
Distribution
describes the shape of the
distribution for example the
skewness of the data.
Display Order
variables can be displayed
alphabetically, or by
ascending or descending
means.
4.
1
Click OK.
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Crosstabs
Selecting Cases to Analyse
Crosstabs are two way tables. They allow you to specify
a row and column variable, and a layer. For example
using educational level as the row and Sex as a layer
would list the educational levels for Females, then
Males as shown below. (If no statistics are defined, a
count of cases is displayed.)
Column
You may want to restrict your analysis to a few specific
cases based on a particular variable, for example only
those aged 30 or less, or female and 20 or less.
Row
s
1.
Choose Select Cases from
the Data Menu.
2. Click on the If condition
is satisfied button.
s
3. Click the If button.
4. Double click on the
variable to be tested.
Layers
5.
Add the comparison
operator.
6. Add the value to test
against.
7.
Statistics
Creating a Crosstab
1.
Click on Continue,
then OK.
A new variable will
have been created
entitled filter_$.
Choose Descriptive Statistics from the Analyze
menu.
2. From the Sub-menu select Crosstabs.
Those cases not
selected will have a
diagonal line across
the row number.
Any analysis will be performed on the selected rows
only.
Comparison operators
To obtain statistics such as Chi Squared, click on
the Statistics button. Tick the statistics required,
then Continue.
The comparison criteria can be an exact match or an
expression such as >100 (greater than 100). If
comparing a string variable the criteria should be
entered in speech marks e.g. = “Hull”
3. Add a minimum of a row and column variable.
Click OK.
In the example below the age variable is used.
Weighting cases
If the data you
have is already in
the form of a table,
it can be weighted
to allow you to
perform simple
statistical tests on
it.
1.
Select Weight Cases from the Data menu.
2. Add the variable to be
weighted by.
Operator
Selects if age is:
=35
Equal to
35
>35
Greater than
more than 35
<35
Less than
less than 35
>=35
Greater than or
equal to
35 or more
<=35
Less than or equal
to
35 or less
~= 35
Not
any value except 35
Removing Selection
3. Click OK.
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Criteria
2
1.
Select Cases from the Data menu.
2.
Choose the All cases option.
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T Test
Non-parametric tests
T Tests compare the means of two samples with a
normal distribution.
If normal distribution cannot be assumed it is said to
be Non-parametric, so there are different tests to
compare means.
Paired sample T-test
1.
Wilcoxon
Select Analyze, Compare Means, Paired Samples T
test.
Used for related (dependent) samples
2. Highlight variables to be compared.
1.
3. Click on the arrow
head to add the
variables to the
Paired Variables
box
Select Analyze, Nonparametric tests, Legacy
Dialogs, 2 related samples.
If the arrowhead is greyed out, make sure you
have two variables selected
4. Click OK and the statistic is displayed in the
Output window.
Independent 2 sample T test
1.
The data must be
entered as value,
group as shown
opposite
2. Highlight the variables to be compared and add to
the Test Pair(s) list.
3. Click OK.
2. Select Analyze,
Compare Means,
Independentsamples T Test.
Mann-Whitney U Test
Is similar to the two sample T-test. It is used for
independent samples.
3. Add the variable(s) whose mean you want to
compare to the Test Variable.
4. The group variable should be added to the
Grouping Variable box.
5.
Click on the Define Groups button.
1.
Select Analyze, Nonparametric tests, Legacy
Dialogs, 2 Independent samples.
2. Add the variable(s) whose mean you want to
compare to the Test Variable List.
3. The group variable should be added to the
Grouping Variable box.
6. Enter the values to be assigned to each group.
4. Click on the Define Groups button.
7.
5.
Click Continue, then OK.
Add the groups required
6. Click Continue, then OK.
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