A Primer on Experimental and Quasi-experimental Design.

Counseling psychology is a relatively new field that is gaining autonomy and respect. Unfortunately, research efforts in the field may lack an appropriate research design. This paper considers some of the more common types of research design and the associated threats to their validity. An example of each design type is drawn from the counseling literature. The three pre-experimental designs explored are the one-shot case study, the one-group pretest-posttest design, and the static-group comparison. True experimental designs yield results that are more trustworthy than the pre-experimental designs because random assignment is used. Three true experimental designs discussed are the pretest-posttest control group design, the posttest-only control group design, and the Solomon four-group design. When a true experimental design in not available for various reasons, the researchers can use a quasi-experimental design. The three major categories of quasi-experimental design are the nonequivalent-groups design, cohort designs, and time-series designs. (Contains 38 references.) (SLD)