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	Blockad Solomon fyrgruppsdesign	Experimentell design med förtest och eftertest
Ämnesområde	Försöksplanering	Försöksplanering
Familj	Process / pipeline	Process / pipeline
Ursprungsår	1949 (base); blocking extension applied in behavioral and social sciences from mid-20th century onward	1963 (formalized in Campbell & Stanley)
Upphovsperson	Richard L. Solomon (base design, 1949); blocking integrated from classical experimental design tradition (Fisher, 1935)	Donald T. Campbell and Julian C. Stanley
Typ	Experimental design	Experimental / quasi-experimental research design
Ursprungskälla	Solomon, R. L. (1949). An extension of control group design. Psychological Bulletin, 46(2), 137–150.	Campbell, D. T., & Stanley, J. C. (1963). Experimental and Quasi-Experimental Designs for Research. Rand McNally.
Alias	Blocked S4G, randomized blocked Solomon design, Solomon four-group with blocking	pretest-posttest design, before-after design, pre-post design, two-wave experimental design
Närliggande	6	5
Sammanfattning	The blocked Solomon four-group design combines Solomon's classic four-group structure — which disentangles pretest sensitization effects from treatment effects — with blocking on a known nuisance variable. Participants are first grouped into homogeneous blocks (e.g., by baseline ability, gender, or site), then randomly assigned within each block to one of four conditions: pretested treatment, pretested control, unpretested treatment, and unpretested control. This structure simultaneously controls for maturation, pretest reactivity, and block-level variance, making it one of the strongest quasi-controlled experimental frameworks available.	The pretest-posttest experimental design measures participants on the outcome variable before and after treatment, typically with random assignment to treatment and control groups. The difference between pre- and post-scores isolates the treatment effect from baseline variation, making this one of the most widely used frameworks in experimental and quasi-experimental research across education, psychology, medicine, and the social sciences.