double blind

Richard DawkinsのThe God Delusionを読んでいます。
神への祈りは本当に効果があるのかどうかをテストで確かめる話です。
Templeton Foundation, to test experimentally the proposition that praying for sick patients improves their health. 36 Such experiments, if done properly, have to be double blind, and this standard was strictly observed. The patients were assigned, strictly at random, to an experimental group (received prayers) or a control group (received no prayers). Neither the patients, nor their doctors or caregivers, nor the experimenters were allowed to know which patients were being prayed for and which patients were controls. Those who did the experimental praying had to know the names of the individuals for whom they were praying - otherwise, in what sense would they be praying for them rather than for somebody else?
祈りの対象となる患者は勿論祈られていることを知らされず、医者や看護師もどの患者が祈られているか知らない状態でテストされることが "double blind" と言うようですが、辞書の説明を見ます。
・Oxford English Dictionary: Denoting a test or trial, especially of a drug, in which any information which may influence the behavior of the tester or the subject is withheld until after the test.: I strongly advise you to conduct proper double-blind tests of any ability you believe you can demonstrate, before attempting to undergo a testing for this prize.
この辞書は "single-blind" についても言及しています。
single-blind: Denoting a test or experiment in which information that may bias the results is concealed from either tester or subject.: Forty consecutive subjects with lipid profile abnormalities were enrolled in a single-blind, placebo-controlled crossover study.