Final answer:
The described study design is a Regression-Discontinuity design, which is characterized by assignment to groups based on a cutoff criterion rather than random assignment.
Step-by-step explanation:
The type of design described is a pretest-posttest program-comparison-group quasi-experimental design in which a cutoff criterion on the preprogram measure is the method of assignment to a group. This is known as a Regression-Discontinuity design. In such designs, participants are assigned to either the experimental or control group based on their score on a pretest measure. That score serves as the cutoff point for assignments.
The main features of a properly designed experiment include random assignment of participants to treatment groups to control for lurking variables, ensuring the groups differ only by the experimental manipulation. In the case of a Regression-Discontinuity design, although the assignment is non-random, it capitalizes on a cutoff point to differentiate between groups. This design is effective for assessing the impact of interventions when random assignment is not feasible or ethical.