A Solomon four-group design is an experimental design method that avoids some of the difficulties of pre-test/post-test design. This testing method involves four test groups, each of which is assigned to be exposed to different components of the testing process. This is used to ensure that no individual component of the testing process has an influence on the results of the testing.
This test design is more difficult to set up, but it usually yields better results because it allows the tester to check and account for biases and outside variables. The standard pre-test/post-test design enables the tester to control the variables for the groups, but this does not account for the testing itself and other variables. The four extra tests performed (beyond just pre- and post-test) are a test without the treatment, but with post- and pre-testing, one with treatment and post-test but no pre-test, and one with only the pre-test.
This experimental design method is particularly useful when it comes to sociological and educational testing. It can be used to determine if the pre-testing and post-testing have any influence on the subjects, as well as the treatment itself. For instance, when testing education, this can be used to determine if a pre-test or post-test influence student performance on actual testing. Students may have a disadvantage due to their exposure to pre- or post-tests, so this method can be used to determine if that is the case.