In marketing their products, drug companies often send gifts to physicians. According to a recent survey, most physic...

Skylar on December 2, 2019

@lerondagates, happy to help!

The survey in the passage found that most physicians believe their own choices are not influenced by the gifts. However, the survey also found that most physicians believe the majority of other physicians are influenced by the gifts.

(C) correctly points out that this is incompatible and that some physicians must be incorrect. This is because, if most physicians are correct in saying that they are not influenced by gifts, then most physicians would not be influenced. In this case, the belief that most physicians hold regarding most other physicians being influenced by the gifts would be false. On the other hand, if the claim that most physicians are influenced by gifts is true as reported by most physicians about most other physicians, then the claim by most individual physicians that they are not influenced has to be false.

In other words, it cannot be simultaneously true that most physicians are not influenced by the gifts (as self-reported by most physicians) and that most physicians are influenced by the gifts (as reported by most physicians about most other physicians). Therefore, it must be true that some physicians are mistaken about the degree of influence.

Does that make sense? Let us know if you have any other questions!

lerondagates on December 2, 2019

Thanks for your response. I understand it a bit. But still unclear. Why can it not be true that most are influenced and most are not? That's what is still unclear to me.

BenMingov on December 2, 2019

Hi Lerondagates, thanks for the question.

I think if we break this down more abstractly, without considering the question itself, might clear this up.

We cannot have two mutually exclusive items applied to the most of the same group. If most of the group (doctors) are influenced (e.g. 51% +) and most of the same group (doctors) are not influenced (e.g. 51% +), then this becomes 102% +.

If we are talking about a single group and discussing the proportion of those influenced vs not, the closest split we can have is 50/50.

For example, if this question was about being in either North America or Europe. Then we cannot have most doctors in North America and most in Europe. That would be more than 100% of all doctors, which is impossible. Going back to the question we are discussing, that is why some must be mistaken.

I hope this helps, please let me know if you have any other questions.

Skylar on December 8, 2019

@lerondagates, let me see if I can add to this briefly!

It cannot be true that most are influenced and most are not influenced because these two conditions are opposites. They are mutually exclusive. In other words, being influenced is the opposite of NOT being influenced.

If I have three physicians and am told that most are influenced, I could conclude that two are influenced and one is not.
If I am then told that most of this same group is not influenced, we would run into a problem because I would want to say that two of the physicians are not influenced. This would leave one physician being both influenced and not influenced at the same time, which is impossible since the two are opposites and therefore contradictory. To understand this, you can think of the passage as posing any other opposite statement- like the physician is both awake and asleep at the same time. These opposite conditions cannot occur simultaneously, which is what (C) points out. I have included a visual diagram below to show this.

Physician 1 Physician 2 Physician 3
Influenced Influenced NOT Influenced = most are influenced (2/3)
Influenced NOT Influenced NOT Influenced = most are NOT influenced (2/3)
= contradictory = 4/3, which is impossible

Does that make more sense? Best of luck with your studies and please let us know how we can help!