I agree with the consensus here. Double blind study will produce a more reliable/unbiased result because the data that will be collected is based solely on observations by the investigators. I think that if the investigator has prior knowledge as to who got placebo or the actual drug can affect their judgment when recording results; because in a way they are looking or waiting for something to happen to the subject that got the actual drug. They can become biased on their approaches to the study for each subject. Also, double blinded studies prevents tampering of results because if the investigator wants a certain result for a drug due to ties, or not so good relationship, with the company conducting the research they can definitely influence the results based on their liking.