Determine whether the following study described is observational or an experiment. If the study is an experiment, identify the control and treatment groups, and discuss whether single- or double-blinding is necessary. If the study is observational, state whether it is a retrospective study, and if so, identify the cases and controls. A national institute's study of 767 melanoma patients and 1048 cancer-free patients matched by age, sex, and race found that those having a single large mole had twice the risk of melanoma. Having 10 or more moles was associated with a 12 times greater risk of melanoma. If the study is an experiment, identify the control and treatment groups. Choose the correct answer below.
A. The control group would be the patients that have at least one large mole and the treatment group would be patients without any large moles.
B. The control group would be the patients without any large moles and the treatment group would be patients that have at least one large mole.
C. The control group would be the patients without any large moles. There would be two treatment groups, one group of patients with a single large mole and one group of patients with 10 or more moles.
D. The study is not an experiment.