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Select cases

Page history last edited by William Kirts 5 years, 3 months ago

 The Select Cases command prohibits from further analysis all those cases that do not meet specified selection criteria.When analyzing a data file in SPSS, all cases with valid values for the relevant variables are used. SPSS provides a function that allows us to separate a subset of cases within a data file.

 

We will introduce the Select Cases command by working through an example that involves the simplest selection standard, which is where we select cases that have a distinct value for a single existing variable.

 

For Example, suppose we have a data set from the Tour de France. We want to be  able to narrow down the Tour de France data set to those cases just from, let's say, Stage 15. This is where Select Cases will help us.

 

 

 

 

 

 

 

This helps us see the data in which we wanted to filter a lot more easier. And as you can see, there is a new variable, in the last column, that is labeled "filter_$". It demarcates the selected cases as 1's. If we do an analyzes on this data, it's only going to do it on those cases that correspond to Stage 15. As you can see it crosses out the Cases, on the left side, that are not associated with the number 15 on the variable we use, which is "Stages".  Also, one should not mess with the filter variable directly. If one wants to change the subsetting condition, one should go back to Select Cases and make the change there.

 

When dealing with outliers, which are defined as extreme values that do not seem to fit with the majority of a data set, Selected Cases helps us remove these outliers from the data.  If not removed, these extreme values can have a huge effect on any conclusions that might be drawn from the data in the question, because they can skew correlation coefficients and lines of best fit in the wrong direction. Therefore, Selected Cases is the command that helps us remove the outliers from the data. 

 

How to Select Cases in SPSS

  • Go to "Data" menu and select "Select Cases"
  • Once in the Dialog Box select "If Condition is satisfied" and then Click on "If..."
  • In the source variable list, select the variable whose values will act as the filter.
  • Either Drag the Variable or click on the Arrow  to move it to the empty space.
  • Once in the box, From the calculator pad or from the keyboard, type in the appropriate numbers. In the example we provides it'd be Stages=15, since it was the variable we would like to select. 
  • Click "Continue".
  • Then Click "OK"
  • After clicking "OK", SPSS will cross out the rows on the left. .

 

 

The following video Illustrates these steps:

 

We might want to run analyses for just Stage 15. Select Cases allows us to do this specialized analysis without deleting the rest of the data, copying and pasting just the data from Stage 15 to a new data set. 

 

 

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