Which of the following is an example of a one-group pretest-posttest research design?
a. A group of depressed patients is compared to a group of non-depressed patients.
b. A group of depressed patients is assessed before they enter a mental health facility and after they leave the facility.
c. The head of a mental health facility that specializes in depression is interviewed.
d. A group of patients who are spending time in a mental health facility are interviewed.