Cuantitatif design

SOLOMON THREE GROUP DESIGN

The first of the solomon designs uses three groups, with random assignment of subjects to groups. You can see that the first two lines of this design are identical to design 5. However, this solomon three-group design has the advantage of employing a second control group and thereby overcoming the diffuculty inherent in design 5 – namely, the interactive effect of pretesting and the experimental treatment. This second control group, labeled C2, is not pretested but is exposed to the X treatment. Their Y2 measures are then used to assess the interaction effect.
The interaction effects is assessed by comparing the Y2 scores for the three group. Only the posttest scores enter intio the analysis. Even thoug the experimental group has a significantly higher mean on Y2 than does the first control group (C1 ), the researcher cannot be confident that this difference is caused by X. It might have occurred because of the subjects’ increased sensitization after the pretest and the interaction of their sensitization and X. However, if the Y2 mean of the second control group (C2 ) is also significantly higher than that of  the first control group, tha you can assume that the experimental treatment, rather than the pretest – X interaction effect, has produced the difference because the second control group is not pretested. This group, although receiving the X treatment, is functioning as a control and is thus labeled C2.