8 Paired samples T-Tests
This activity introduces the paired samples t-test. It is also known as the ‘repeared measures’, ‘within participants’ or ‘related’ t-test. It is used when your design is within participants, i.e. where participants contribute data for the dependent variable in all conditions. If participants were to contribute to two conditions, for example an experimental and control condition, then a paired samples t-test is used.
Remember that there are two variants of the t-test:
paired samples t-tests.
Data files are set up differently according to which t-test is chosen. In addition there are separate menus in SPSS for each type of t-test. Finally, each t-test will produce different outputs.
They are often used in ‘pre-post’ designs where measures of the same dependent variable are taken both before and after some intervention. Comparisons are then made between the pre and post data to see how effective the intervention has been.
Once again, it is important to remember that there will be one independent variable – with two conditions, for example:
pre and post;
condition 1 and condition 2.
Please observe that the same participants are providing the data for each condition. This is a requirement for using the paired samples t-test.
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You can download this SPSS file from this tutorial here.