The patient then waited through an extended period for healing. Then, in a surgery similar to those done to create vaginas for intersexed patients, surgeons constructed the patient's vagina by using skin grafts taken from her thighs or buttocks (Christine's vaginoplasty surgery was in 1954).
Experimental and quasi-experimental research designs. Ph.D. In an experimental design, subjects are randomly assigned to groups for different levels of treatment (or no treatment, i.e., the control group). In a quasi-experimental design, subjects are not randomly assigned to treatment; there is no randomization. Random assignments of subjects helps control for participant differences, one of the main sources of threats to internal validity of a research study.
A type of quasi-experimental design that is generally better than either the nonequivalent groups design or the pretest-posttest design is one that combines elements of both. There is a treatment group that is given a pretest, receives a treatment, and then is given a posttest. Quasi-experimental research involves the manipulation of an independent variable without the random assignment of participants to conditions or orders of conditions. 2  Among the important types are nonequivalent groups designs, pretest-posttest, and interrupted time-series designs.