From Science Blogs:
You could measure how much money the Tooth Fairy leaves under the pillow, whether she leaves more cash for the first or last tooth, whether the payoff is greater if you leave the tooth in a plastic baggie versus wrapped in Kleenex. You can get all kinds of good data that is reproducible and statistically significant. Yes, you have learned something. But you haven’t learned what you think you’ve learned, because you haven’t bothered to establish whether the Tooth Fairy really exists.
There’s a lot of tooth fairy science out there right now. It’s been increasing in quantity ever since the rise of so-called “complementary and alternative medicine” (CAM), now known as “integrative medicine” over the last two decades. “Energy healing,” acupuncture, homeopathy, craniosacral therapy, reflexology, even faith healing, there’s no pseudoscience too ridiculous to be excluded from pointless clinical trials. What all these clinical trials share in common is that they are tooth fairy science. They study a phenomenon without its ever having been established that the phenomenon actually exists. Worse, because of the vagaries of he clinical trial process, bias, and even just the random noise in clinical trial results that produce seemingly positive trials by random chance alone, advocates of these pseudoscientific treatments can always point to evidence that their treatment “works.” The overall body of existing research on a treatment like homeopathy is negative, but homeopaths can always cherry pick individual studies and sound convincing doing it.
More here.