Solomon four-group design explained

The Solomon four-group design is a research method developed by Richard Solomon in 1949.^[1] It is sometimes used in social science, psychology and medicine. It can be used if there are concerns that the treatment might be sensitized by the pre-test.^[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.

Structure

The structure of the trial is shown in the table :

The four groups in the Solomon design
Group	Pre-intervention	Intervention	Post-intervention
1	Test	Treatment	Test
2	Test	Control	Test
3	No test	Treatment	Test
4	No test	Control	Test

The first two groups receive the evaluation test before and after the study, as in a normal two-group trial. The second groups receive the evaluation only after the study.

The effectiveness of the treatment can be evaluated by comparisons between groups 1 and 3 and between groups 2 and 4.. 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.^[3] ^[4]

Notes and References

Web site: Navarro . Mario . Siegel . Jason T. . Solomon Four-Group Design . "The Solomon four-group design, developed by Richard Solomon in 1949, was devised to overcome the problem of pretest sensitization." . 2018 . 22 November 2019 . SAGE Publications.
Introduction to Research in Education by Donald Ary, Lucy Jacobs, Christine Sorensen
Web site: Sawilowsky, Shlomo S.; Markman, Barry S. . Another Look At The Power Of Meta-Analysis In The Solomon Four-Group Design . . "This paper demonstrates that a meta-analysis technique applied to the Solomon Four-Group Design (SFGD) can fail to find significance even though an earlier 'weaker' test may have found significance." . 1988 . 22 November 2019.
Sawilowsky, Shlomo S.; Kelley, D. Lynn; Blair, R. Clifford; Markman, Barry S. . Meta-Analysis and the Solomon Four-Group Design . The Journal of Experimental Education . . "The present study is a Monte Carlo demonstration." . 1994 . 62 . 4 . 361–376 . 10.1080/00220973.1994.9944140 . 20152427 .