"Now, you have your two things that you think will help the sick people get better. Give one to the people in group one, and the other to the people in group two.
"If you can, it’s a really good idea to make sure that the sick people don’t know which group they are in, or what they are having to make them get better. The same is true for the people working on the problem.
"This is for a good reason: we have found that people get better faster when they think they have been given something that works well to make them feel better, even if they haven’t really.
"Now: you know what is wrong with your sick people, so you know how long it will take for them to get better. Wait a while, and then look and see if people get better faster (or more better!) in group one, or group two. This will tell you which of the things that you did helped people the most.
"Looking at a big number of sick people will help you to be sure that you have got the right answer. If you have friends who have tried the same idea, you can add their numbers to your numbers and get an even clearer idea of what works best.
"Don’t let anyone hide their numbers!"
Ben Goldacre, a doctor/researcher who writes about problems in science