Determine whether the following study is an observational study 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 case-control study, and if so, identify the cases and controls. In a study of the effects of magnets on back pain, some participants were treated with magnets while others were given nonmagnetic objects with a similar appearance. The magnets did not appear to be effective in treating back pain. Choose the correct answer below.
A. Experiment, the treatment group is patients that used the magnets and the control group is patients that received the placebo; double blind
B. Observational study; case control; the cases are the patients that received magnets, the controls are the patients that received placebos
C. Observational study; not case-control
D. Experiment, the treatment group is all patients and the control group is patients that received the magnets; single blind