What is partially blinded clinical trial?

A blind in a clinical trial means that one party doesn't know what is being tried. For example, if a scientist wants to check the efficacy of a drug, a blind in this case would means that the person who conducts the trial wouldn't know which is the drug and which is the placebo. This was a single blind trial. A double bling would imply that the scientist doesn't know which research group gets which component. The purpose of blinds is to not allow human expectations to project onto the results. If a scientist expects a certain result, he will somehow see it and so to remove the error that could be caused by such a misinterpretation, most trials are partially blinded. The results from such trials are said to be unbaised because they are reported as is.