[1] It is sometimes used in social science, psychology and medicine.
[2] In addition of the usual two groups (treatment and control), it has a second pair of groups who do not receive a pre-intervention evaluation.
The structure of the trial is shown in the table :[citation needed] The first two groups receive the evaluation test before and after the study, as in a normal two-group trial.
In addition, the effect of the pre-treatment evaluation can be calculated by comparing the control group who received the pre-treatment evaluation with those who did not (groups 2 and 4).
Various statistical treatments for the Solomon four-group design have been put forward, including Stouffer's Z and Monte Carlo.