McKinley: A double-blind study, in which neither the patient nor the primary researcher knows whether the patient is being given the drug being tested or a placebo, is the most effective procedure for testing the efficacy of a drug. But we will not be able to perform such a study on this new drug, since the drug will have various effects on the patients' bodies, which will make us aware of whether the patients are getting the drug or a placebo. Engle: You cannot draw that conclusion at this point, for you are assuming you know what the outcome of the study will be. Engle's statement indicates that he is most likely interpreting McKinley's remarks to be ["referring to the drug's therapeutic effects rather than to any known side effects", 'presuming that a double-blind study is the only effective way to test new drugs', 'based on a confusion about when a drug is efficacious', "presuming that the placebo will produce no effects whatever on the patients' bodies"]