SPSS Statistics

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How to do within-subject analysis with two datasets (pre and post)

  • 1.  How to do within-subject analysis with two datasets (pre and post)

    Posted Thu October 28, 2021 09:29 AM
    Hi, 

    I am fairly novice with SPSS so would welcome some advice. I have two datasets that capture the same measures from the same people before and after - a Pre and Post study. I have managed to merge by cases, which allows me to do a general comparison of pre and post scores. However, I want to look at within-subject change and I can't see how to match up the cases to allow me to do this, or whether there is another way of comparing pre and post scores for each case. 

    Each participant has an ID code (though people didn't always use the same one each time so there are a few cases that need to be deleted due to no matching data), and each dataset is coded 1 for pre and 2 for post. When I merge by variables (labelling them Measure1PRE, Measure1POST and so on), the post scores still come up as separate cases, just with empty cells under the PRE variables. Ideally I want the data all in one row for each case: 

    ID     Measure1PRE    Measure 2PRE Measure 3PRE Measure1POST  Measure2POST and so on. 

    If I can't organise the data like that, is there anything I can do to carry out the analysis that way? 

    Sorry if this is confusing - I'm just not sure how to calculate within-subject analysis ... and would welcome help.  
    (there are several hundred cases so I can't manually calculate them either)

    Thanks.

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    Carly Butler
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  • 2.  RE: How to do within-subject analysis with two datasets (pre and post)

    Posted Thu October 28, 2021 09:32 AM
    Hi. Can I please see the MATCH FILES syntax you used? The BY variable(s) must be identical in the datasets being matched. If they are, the variables should line up just as you want them (VAR1_PRE, VAR1_POST).

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    Rick Marcantonio
    Quality Assurance
    IBM
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