#25 - McKinley: A double blind study, in which neither the

[Haleyeastham]

Can you please explain the answer choice to me? I am having difficulty seeing how therapeutic vs side effects applies.

Thank you!

[Steve Stein]

Hi Haley,

That's a great question, which requires us to think about how Eagle construes McKinley's statements: McKinley says that a double-blind study is not possible in the present case, because the various effects will make it clear to the researchers which patients are getting the drug.

Eagle says McKinley is assuming knowledge of the study's outcome; Eagle thinks McKinley is referring only to the drug's intended effects--the argument under this interpretation would go something like this:

"We can't do a double-blind study on this new headache medicine, because researchers will know which patients are getting the drug, since those patients will be the ones whose headaches are being cured." Such an argument would have to presume that the drug effectively cures headaches, before the study testing the drug's effectiveness has even been conducted.

But McKinley says that the new drug will have "various effects" on the patients' bodies, which may include the intended therapeutic effects (headache reduction, for example), but may include side effects as well. So, we wouldn't have to make any assumptions about whether or not the drug were necessarily effective in order for the researchers to be able to tell the drug-takers from the placebo-takers; the appearance of known side-effects could be the give-away, even without knowing anything about the effectiveness of the drug.

For example, if the drug's effectiveness is unknown, but a known side effect is the temporary appearance of a rash on the arm, then it would be possible for researchers to determine who is getting the drug without having to make any assumptions about the drug's effectiveness as a pain-reliever.


Tough question--I hope that's helpful! Please let me know whether this is clear--thanks!

~Steve

[al_godnessmary]

I eventually got this right, but I was hoping for someone to walk through the reasoning process with me.

I struggle between C and D.

Originally I thought it was C because if the placebo has NO effects, but the drug does (whether therapeutic or side effects), it would be noticeable and therefore give away the status of the substance taken. When McKinley says the study will be impossible because "we would know" - this choice fits the bill! When I came back to the question I thought that the "outcome" of the study cannot refer to the effect of the placebo (we KNOW that the placebo is, well, not going to physically cause any difference in the patients' bodies...and maybe psychologically induced improvements or changes shouldn't come into this conversation at this point?)...and therefore eliminates C?

D - I debated over this one a lot, because I didn't see why it makes such a big difference if Engle assumes that McKinley is talking about side of therapeutic effects. The only conclusion I could come to about this is that Engle assumes McKinley is talking about the fact that the drug will CURE the patients and therefore it will become evident that the placebos are placebos, rather than the drug will cause negative side effects that the placebos won't cause, thereby giving itself away. I feel like the moment of clarity with the realization of this reasoning comes and goes, so I don't feel I understand it properly yet...

[Emily Haney-Caron]

Hello, and thanks for the question!

Your reasoning for D is spot on. Good work thinking it through! The key here is noticing that Engle says, "you are assuming you know what the outcome of the study will be." The outcome of the study would be the efficacy of the drug (meaning how well it works compared to the placebo), so Engle thinks from McKinley's statement that McKinley is saying he would know whether the patients are taking the drug or a placebo based on whether they get better (whether the drug works)--that is the change in their bodies Engle (probably incorrectly) thinks McKinley is talking about. But actually, it is possible McKinley means that the drug will have side effects, so he would know which patients (the ones with side effects) were taking the drug.

Does that help make D a little more concrete for you?

[al_godnessmary]

Thanks! It took a lot of head-scratching but your answer helps me wrap it around my head more firmly, so to speak!

[DlarehAtsok]

I am also having a hard time with this one. In my opinion there are two keywords here, "we" in the question stem and "known" in answer choice (D). The double-blind study will not work because doctors, not patients, will be aware of "something". So, it must be about the therapeutic effects, given that the known side effects are also known by patients and could be induced even if they take the placebo. For example, say one known side effect is headache. The patient, aware of it, could claim a headache even if he/she took the placebo pill. From this (C) would be eliminated. I believe that Engle's statement indicates that McKinley assumes that the therapeutic effects of the drug will be effective. We don't have as an answer choice the efficiency part ((B) is the exact opposite), so we must go with (D).

[Adam Tyson]

I think it may be a bit of a stretch to say that patients will also know what those side effects are - the use of "known" in answer D is a bit vague on that point. If the effects that McKinley is referring to are known side effects, they still could be known only to the researcher and not revealed to the patients. If McKinley was referring to the therapeutic effects (the patients condition improves), then Engle's reply would make sense - McKinley could only make that claim if he knew that the drug would work and the placebo would not (something we can't know until we do the study - that's the whole point of doing the study). If, however, McKinley was referring to side effects, then at least his argument could make sense and Engle's reply might be less relevant, if at all.

I think you raise a good point here - if the patient also knows the side effects, then McKinley's claim is still not great and Engle's reply makes some sense. Then again, what if the known side effects are things like purple urine or sprouting tiny wings? In that case, where it would be unlikely that a placebo could produce such effects, then McKinley's argument becomes a little better and Engle's reply gets downgraded. That's why, giving Engle the benefit of the doubt, we can assume that he is probably referring to the therapeutic effects rather than side effects.

Ultimately, we are not looking for an answer that proves anything. Engle doesn't HAVE to be thinking about therapeutic effects, but it seems LIKELY that he is. The stem asked what was likely, and of all the answer choices D is the best match for what he PROBABLY had in mind.

[mN2mmvf]

I don't quite understand why referring to the "outcome" of the study implies a focus on therapeutic effects. If there are known side effects to the drug, why can't observing those side effects be an outcome, whether or not the therapeutic effect occurred?

[Eric Ockert]

The first sentence says that "A double blind study.....is the most effective procedure for testing the efficacy of a drug." The stimulus goes on to refer to "such a study." So the "outcome" of such a study would be to determine the efficacy or effectiveness of the drug. Basically, how well does it work? That is more or less referring to therapeutic effects.

Hope that helps!

[bengs49]

Hi PowerScore team -- thanks for all the responses to others, this is very helpful.

I was wondering if there is a way we can abstract any more general learnings from this to improve -- would the key to success here be to "word match" (e.g., "testing the efficacy" in stimulus corresponds to "therapeutic effects" in answer?)

Similarly open-ended question: Do any questions similar to this one come to mind? It would be great to "drill" on similar nuances within LR (not just this question type specifically )

Thanks much!