One of the hardest hypotheses to test today is the theory that magnets can cure a surprising range of diseases and disorders, and part of it is ruling out the placebo effect. The placebo effect occurs when any treatment at all, even one that clearly has no effect (like giving the patient a sugar pill) still cures their disease because the patient expected it to happen. "I got treatment because people care about me" is a powerful thought to a person who is ailing. To rule out the placebo effect, most clinical trials do a double blind study. Neither the patients nor the doctors administering it know which is the real treatment, and which are a fake chalk tablet that only gives the impression that you're getting powerful drugs. And here's where we have the problem.
Any American who graduated the fifth grade, basically all of them, know how to tell the difference between a magnet and an inert chunk of iron. If you press it against metal and the metal sticks, it's a magnet. If you bring it up to a TV and the picture distorts, it's a magnet. If it deflects a compass needle, it's a magnet. The double blind will be ruined, I guarantee. The people with the fake magnets will find it obvious.
If we can resort to some very totalitarian methods, and we can because this study will pay handsomely and "scientific firm reserves the right to dickishly control every aspect of your life for the duration of the study" will be in the contract, if not in those exact words. If you've ever seen the X-men movie, the scene where the villain Magneto is imprisoned in a plastic bubble suspended by fiberglass line, because of his ability to control basically any piece of metal anywhere near him makes imprisoning him in a tradition prison stupid, inspires the perfect impossible-to-detect-magnetism environment ever. You will live in an all plastic and ceramic environment with no metal or electricity. You are encouraged to bring books, writing materials like pencils and paper, and metal-free hobby things. All metal or electronic devices will be confiscated for the duration of the study. You will have a device with something heavy and metal-ish sewn into a cloth pocket strapped onto you. Half of these will contain an actual magnet. The other half, an inert piece of metal of the exact same size, shape, and weight. Participants will journal their recovery from disease over the course of two weeks to a month. We will also have to keep you isolated from each other, except for maybe a ceramic-can-on-a-string telephone. We can't run the risk that you'll "test" each other's "magnets."
After the study is over, we can then reveal who actually had a magnet, and who had just a chunk of metal. And we will finally have determined if magnet therapy offers any actual benefit, or is just another attractive woo-woo claim.