When people show signs of having a heart attack an electrocardiograph (EKG) is often used to diagnose their condition...

Zach on June 6, 2018

Why C?

Why is C the correct answer?


Christopher on June 11, 2018

@zcrabill, this is a weaken question, so you're looking for information that would interrupt the logical flow from the given premises to the conclusion. These typically will not directly attack the information in the premises but will challenge the interpretation or give an alternate explanation for a piece of information.

In this question the argument hinges on the premise that the EKG computer correctly diagnosed a higher proportion of the cases that were later confirmed to be heart attacks than its human counterpart. Given that information, the author concludes that the EKG computer is more reliable and should be used rather than human cardiologist to diagnose heart attacks. You've got to assume that the data points are true, so the EKG computer did, in fact, correctly diagnose more heart attacks, so looking at the answers, which would challenge the logical progression from this premise to the conclusion?

(A) Doesn't interact with the premise or conclusion at all, so this is wrong.

(B) This is anecdotal and doesn't help shift the conclusion. While this sentence contradicts the conclusion, it does not impact the logical progression presented in the argument. Since it opposes but does not weaken the argument, this is not the answer.

(C) This provides an alternate explanation for the data. By saying that the cardiologist correctly diagnosed significantly more cases that were not heart attacks suggests that the EKG computer identified more heart attacks because it had a tremendous number of false positives. If this is the case, then it no longer makes logical sense to move from the earlier premise to the conclusion, thus (C) weakens the argument.

(D) This is likely true, as the argument refers to a process by which the cases were later confirmed to be heart attacks or not. Since this is likely true anyway, it has no impact on the logic of the argument.

(E) Since the argument describes the cardiologist as very experienced and highly skilled, if he or she is unrepresentative of most cardiologists, then the advantages that the EKG computer displayed should be more pronounced against the representative cardiologist. This does not weaken the argument (may even strengthen it) so is not the answer.

Does that help?