Basic data operations in SPSS - ISS - University of Leeds

Basic data operations in SPSS for Windows 17
Version 6 (November 2009)
3 Working with subsets of data
A common requirement in analysis is to be able to analyse subsets of data.
SPSS allows selections to be made on either a temporary or permanent basis. Temporary selections are
performed using a filter. When filtering is active, all cases remain in the data editor window but only those
cases filtered are used for analysis. If permanent selection is used, cases not included in the selected subset
are deleted from the data editor window.
If only a few analyses are to be carried out on subsets, filtering would be the best approach. However, if
extensive analysis is to be performed on a selected subset, it would be more efficient to use a permanent
selection. If permanent selection is used, however, it is advisable to save a copy of the selected data to a new
SPSS system file before proceeding with analysis. This will protect against the danger of saving the data to the
original SPSS data file, with a resultant loss of data.
Data selection is performed using the Select Cases facility on the Data menu.
When the same analysis is required for more than one subset of data, the repeated use of the Select Cases
facility can become tedious. If the data set contains a variable whose values identify the multiple subsets, the
Split File facility can be used instead to reduce the effort in carrying out the analyses on multiple subsets.
Task 10 Selecting a subset of cases
Objective To select a subset of data cases for analysis.
Comment This illustrates the use of a temporary selection or filter.
Problem The data file census.sav contains information relating to individuals. It is required to restrict
analysis to individuals who are unmarried and earning at least £20,000 per annum.
Activity 10.1 Open the SPSS data file census.sav.
Activity 10.2 Select Select Cases from the Data menu. The Select Cases dialog window will be displayed.
Figure 33: Select Cases dialog window
Note the different ways in which cases may be selected.
The choice ‘If condition is satisfied’ restricts cases to those satisfying a logical condition
entered by the user. The next choice, ‘Random Sample of Cases’, selects a random subset of
cases based on a pseudo-random number generated by SPSS. The third option allows case
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