Atherapist believes so strongly in her approach that she finds improvement even when none exists. which design would prevent this problem?

In the scenario in which the therapist believes so strongly in her approach that she finds improvement even when none exists the double blind design would prevent this problem. In the double blind design the subjects (the participants and the experimenters) do not know which group they are in, which means they are unaware of the nature of the treatment, they do not know who is receiving a particular treatment.