wat is a double blind placebo controlled study?

Answer 1

This means that some people are given a placebo instead of the actual drug being tested. Double blind means that the neither the test subjects nor the test administers are aware of which subjects received the placebo. Not until after the tests are done anyways.

Answer 2

"Placebo-controlled" means that there are two groups of subjects: those receiving what's being tested (e.g. an experimental drug), and those receiving a placebo, which is similar to what's being tested but has no active ingredient or action. In, for example, drug studies, the placebo is a sugar pill. The problem with research on people is that subjects have a tendency to feel improved with any kind of treatment, no matter what. This is commonly called the "Placebo Effect." By having a placebo in a study, the researchers can tell how much improvement is due to the effect of what is being tested, and how much is due to the Placebo Effect.

"Double blind" means that neither the test subject nor the evaluator knows if the subject is taking the placebo or the active drug (a third party keeps track of who is receiving what, and only reveals it after the study is completed). This helps to avoid "rater bias," which is when the person who is doing the testing has a tendency to unconsciously rate the subject as improved when he knows the person is receiving the active treatment (as opposed to the placebo). Likewise, when the subject knows, for example, that he is receiving the placebo, he has the tendency to minimize any difference.

Double-blind, placebo-controlled studies are really the gold standard in scientific research.