In a study of the effect of magnets on back pain, 150 subjects were treated with magnets while 150 others were given non-magnetic devices with a...

In a study of the effect of magnets on back pain, 150 subjects were treated with magnets while 150 others were given non-magnetic devices with a similar appearance. After a week of treatment, subjects reported their level of back pain (Journal of the American Medical Association).

What are the treatment and control groups?

Is the experiment placebo controlled? How can you tell?

Would it be possible for the experiment to be double blind? Explain.