A psychiatrist randomly selects 10 patients from her therapy practice to take part in a study that will look at the effects of a new antipsychotic drug. She assigns the patients with the more severe psychotic features to the treatment group and the patients with the less severe psychotic features to the control group. After six weeks she assesses the psychotic symptoms of all of her patients. This is an example of a(n): 

simple interrupted time-series design. 

posttest-only design with a nonequivalent control group. 

pretest-posttest design with a nonequivalent control group. 

one group post-test design.