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Analyses using SPSS version 19
Chiara Haller, Harvard University
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Objectives
Knowledge:
– How to use statistical analyses logically
– How to create/structure a dataset
– How to clean up the dataset
– How to create frequency tables
– Descriptive statistics:
– Graphs (box-plot, dispersion diagrams)
– Stratify the analysis
Literature: Introduction to SPSS (Andy Field)
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Data acquisition
Name Date of Birth Weight/height Sex
Type it directly into SPSS? Into Excel and - Import the data
- Copy the data into SPSS
Whatever you decide, keep a back up of your original dataset!!
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Missing data
Input a value which must not be confused with any other value.
For example giving it a coding which does not exist in the rest of
the data (i.e., -99).
Attention: Don’t forget to tell SPSS that these are missings!
means without correct coding
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The Computefunction
Calculate scores on
behalf of existing
variables
Example: Calculate
BMI on behalf of the
variables weight and
height
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Commande RECODE
Recode Variables
Example: Recode
height into 3
categories
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The syntax
It’s possible to keep all the analyses in a file Instead of OK, press PASTE, and your commands are being
opened as syntax, which can now be saved.
There are 3 windows you work with on SPSS:– Dataset: Variable view, data view– Output– Syntax
Each of these windows can be saved.
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Descriptive statistics
Mean
Variance / standard deviation
Minimum / Maximum
… (click options for more)
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Box-plot
Minimal Value
Mediane
Lower quartile (1st quartile
Upper quartile (3rd quartile)
Extreme Values
¼ (top 25%)
¼
¼«interquartile range»
¼ (bottom 25%)
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Scatter Plot
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Stratify the analysis
It is often useful to split a sample in several sub-samples
Three possibilities:– Split the file– Select the preferred observations– Perform the analysis by stratifying the variable
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Split files
Exercise:
Re-analyze the descriptive statistics
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Select the preferred observations
Exercise:
Re-analyze the descriptive statistics
THE END
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