Dr. A: The new influenza vaccine is useless at best and possibly dangerous. I would never use it on a patient.
Dr. B: But three studies published in the Journal of Medical Associates have rated that vaccine as unusually effective.
Dr. A: The studies must have been faulty because the vaccine is worthless.
In which of the following is the reasoning most similar to that of Dr. A?
(A) Three of my patients have been harmed by that vaccine during the past three weeks, so the vaccine is unsafe.
(B) Jerrold Jersey recommends this milk, and I don’t trust Jerrold Jersey, so I won’t buy this milk.
(C) Wingzz tennis balls perform best because they are far more effective than any other tennis balls.
(D) I’m buying Vim Vitamins. Doctors recommend them more often than they recommend any other vitamins, so Vim Vitamins must be good.
(E) Since University of Muldoon graduates score about 20 percent higher than average on the GMAT, Sheila Lee, a University of Muldoon graduate, will score about 20 percent higher than average when she takes the GMAT.

B for me too.

'B'

It has to be C. B is a trap answer. Was the doctor ever malinfluenced by another doctor? Not that we know of.

For me C is the correct answer. The argument is that the studies must be faulty because the vaccine is useless. This is an anormal way of thinking. The normal way would be to reach a conclusion about the utility of the vaccine from studies. The author is actually reversing cause for effect. The same is happening in C.

It's a clear case of circlular reasoning: It is useless. The study says it's good must be wrong because it is useless.

(A) Three of my patients have been harmed by that vaccine during the past three weeks, so the vaccine is unsafe.
Faulty reasoning, basing conclusion on insufficient samples. But not circular reasoning.

(B) Jerrold Jersey recommends this milk, and I don’t trust Jerrold Jersey, so I won’t buy this milk.
Faulty reasoning. Gratuitous criticism. Doesn't base the conclusion on facts, but base it on credit or discredit of the recommender. Not circular reasoning.

(C) Wingzz tennis balls perform best because they are far more effective than any other tennis balls.
"They are the best among everybody because they are better than everybody else." Circular reasoning.

(D) I’m buying Vim Vitamins. Doctors recommend them more often than they recommend any other vitamins, so Vim Vitamins must be good.
Again gratuitous assumption.

(E) Since University of Muldoon graduates score about 20 percent higher than average on the GMAT, Sheila Lee, a University of Muldoon graduate, will score about 20 percent higher than average when she takes the GMAT.
Ecological fallacy. Conclusions obtained from a community or group cannot be directly applied to individuals.

It will be very useful to master these different types of reasoning errors, for both CR questions and your AWA test.
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