Determine whether the following study is an observational study or an experiment. If the study is anexperiment, identify the control and treatmentgroups, and discuss whethersingle- ordouble-blinding is necessary. If the study isobservational, state whether it is acase-control study, and ifso, identify the cases and controls.

In a study of the effects of magnets on backpain, 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.

Observationalstudy; notcase-control

B.

Experiment; the treatment group is all patients and the control group is patients that received themagnets; single blind

C.

Experiment; the treatment group is patients that used the magnets and the control group is patients that received theplacebo; double blind

D.

Observationalstudy; casecontrol; the cases are the patients that receivedmagnets, the controls are the patients that received placebos