# 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.

## Activity 7

0h 20m

Remember that there are two variants of the t-test:

- independent 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.

### Hint

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.

Warning – these tutorials sometimes don’t display properly in Google Chrome. This is a common issue that occurs when Chrome’s ‘Use hardware acceleration when available’ option is switched on. This option is enabled by default, however disabling it should correct this problem. To do this, click on the three dots in the top right corner of the Chrome browser, select 'Settings’ and then ‘Advanced Settings’ at the bottom. Turn off this option underneath the ‘System’ heading, and then close down and restart Chrome. Alternatively, using a different browser should allow you to view the tutorials properly.

You can download this SPSS file from this tutorial here.

OpenLearn - Getting started with SPSS
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