In clinical trials of new medicines, half of the subjects receive the drug being tested and half receive a physiologically inert substance—a placebo. ██████ ███ ████████ ████ ███ █████████ ████ ███████ ████████ ███ █████████████ ████ ████ ███ █████ ████████ ███ ████████ █████ █████ ███ ████ █████ ███████ ████████ ████ █████████ ██ ██████████ ██████████ ███████ ████████
The stimulus gives us an incomplete argument, which concludes that in clinical trials of new drugs, the intention that neither experimenters nor subjects learn who gets the real drug and who gets a placebo is often frustrated. In other words, it's frequently the case that experimenters and/or subjects are aware who gets which treatment, because... why?
Our goal here is to fill in the blank with supporting evidence. The correct answer will give us some reason that explains how experimenters and/or subjects find out who's getting the real drug and who's getting a placebo. This could be through some kind of malfeasance—perhaps experimenters are so curious they look through confidential records to find out. Or it could be due to an effect of the real drug that subjects and/or experimenters notice. Either way, the correct answer will tell us how anyone finds out.
Which one of the following, ██ █████ ████ █████████████ █████████ ███ ████████████
often the subjects ███ ███████ ███ ████ █████ ██████ ███████ ████████ ████ ███ █████████████ █████████ ██ ████ ███████ ██ ███ ███████████████ ██████ ████
(A) describes one way that experimenters can tell apart who's getting the real drug, despite the careful study design. This explains the conclusion, and so it's the support we need to fill in the blank.
subjects who believe ████ ███ █████████ ███ ████ █████ ██████ █████ ███████ ████████████ ██ █████ ██████████ ██████████ ██ ███████ ████ ██ ████████████ ██ ████ ██ ███████████████ ██████ ██ ███
(B) tells us we get a similar result for both groups, whether they receive the real drug or a placebo. That actually eliminates a possible explanation for how subjects or experimenters can tell who's getting what. (B) does the opposite of what we need.
in general, when ███ █████ ██ ████████ ██ █████████ ███ ████████████ ████████ ██████ ██████ ████ ███ ██████████████ ███ ██ ███ ████████ ███ ███████ ██████████
So some clinical trials are limited to healthy volunteers... so what? (C) doesn't have any clear connection to how experimenters or subjects can tell who's getting the drug and who's getting a placebo.
when a trial ████ █ ████ █████ ███ ██ ███ █████████████ ████ ████ ██ ██ ████ █████████ ██ ██████████
(D) could be useful if we knew that experimenters at some stage of a trial could become aware of who's getting what treatment. But since it doesn't say that, (D) does nothing to explain the conclusion.
the people who ███ ████████ ███ ████████ ██████ █████ ██ ████ ██ ██████████ ███ ████ ██ ████████ ██ ███ ███████████ ████ ████ ████ ███████ █ ███████
All the volunteers know they might get a placebo—but that doesn't mean they can tell what treatment they actually get. For (E) to be correct, we would need to baselessly assume that knowing you might receive a placebo lets you reliably distinguish drug effects versus placebo effects.