A Multiplist Strategy for Strengthening Nonequivalent Control Group Designs

Evaluation researchers are often confronted with less than optimal conditions in which to design studies. When this occurs, researchers may be forced to utilize relatively weak designs that do not rule out all threats to internal validity. Using archival data from a sales campaign for a state lottery, this article illustrates a multiplist strategy (Cook, 1985) in which several complementary designs are utilized to help rule out the four threats to internal validity associated with the frequently utilized nonequivalent control group design. Specific methods for addressing each of these threats and strengthening the basic nonequivalent control groups design are also illustrated.