I believe that double is more important than single blind because there would not be anyone altering the experiment. Neither the person being tested and the tester won’t know who is being tested which there won’t be any favorites. The experiment outcome will reliable and true because it is a random experiment. There is bias when the tester has the power to decide who will take the product by just judging the participant look, attitude, sex, age, etc. It good to not know because it not going to be the testers fault if the experiment fail/succeed, the reason being is that they just are observing they didn’t touch anything.