Care to give examples of something 100% provable where results came back 50-50 with a double blind test? How can you skew bias when you have no idea what is being tested. That makes no sense.
Double blind tests are nothing more than a parlor trick, right up there with seances. You can take something 100% provable and subject people to a DB "test" and come back with 50-50 results. All it proves is that uncertainty increases under the guise of testing. Bias is never eliminated but skewed for all the wrong, unanticipated reasons.