For each of the abstracts indicate whether the research design is experimental or observational. If Observational, which one (Cross sectional study, Retrospective or prospective study)?
A. An independent researcher tested the effectiveness of the Atkins weight loss program by randomly selecting 1000 subjects using the program. Each of the subjects was called to report his or her weight before the diet and after the diet.
B. Phase II of the Nurses’ health Study was started in 1989 with 116,000 female registered nurses. This study is ongoing.
C. Sample of subjects with and without heart disease were selected, then researchers looked back in time to determine whether they took aspirin on a regular basis.
D. Researchers from the National Institutes of Health want to determine the current rates of marijuana consumption among adults living in states that have legalized the use of marijuana. They conducted a survey of 500 adults in those states.
E. The Physicians’ health Study involved 22,071 male physicians. Based on random selections, 11,037 of them were treated with aspirin and the other 11,034 were given placebos.