Q13 - A new screening test has been

[Laura Damone]

Question Type:
ID the Flaw

Stimulus Breakdown:
Conclusion: Justine has syndrome Q. Premises: there's a new test that gives a positive result whenever someone has the syndrome. Justine shows a positive result on that test.

Answer Anticipation:
Conditional logic, specifically the application of a principle, is the driver of this stimulus. As such, diagramming, or rephrasing the conditionals into if/then format, might be useful. The first premise tells us that if you have the syndrome, you'll show positive on the test. The second premise tells us that Justine showed positive on the test. The argument concludes that she must have the syndrome. This is a classic Illegal Reversal.

Correct answer:
A

Answer choice analysis:
(A) Here it is, but boy is it a lot to untangle. Correct answers describing Conditional Logic Flaws are often framed in terms of confusion. Sometimes they'll talk abstractly about confusing a necessary and sufficient condition. Other times, they'll say the argument confuses an actual statement the argument made for a statement the argument didn't make but seems to have assumed. This latter format is the one answer choice A takes. The argument actually said when the syndrome is present, you'll test positive. But to reach the conclusion that Justine has the syndrome, the argument seems to have assumed that anyone who tests positive has the syndrome.

(B) Wrong. The accuracy of the test is established as a premise. As such, we don’t need any justification. We just accept that the premises are true.

(C) This argument follows a trajectory from testing positive to having the syndrome. Someone not testing positive isn't treated as though it implies they don't have the syndrome.

(D) The premises establish that when the syndrome is present, the test yields a positive result. That could reasonably be applied to the case of any individual who has the syndrome; going from the general to the specific isn't the problem with this argument. The problem is that the argument reverses the premise before applying it to an individual case.

(E) No reliable results? Rubbish! Our premises establish reliable results whenever the syndrome is present.

Takeaway/Pattern:
Conditional Logic Flaws abound in ID the Flaw questions. Unfortunately, spotting one doesn’t always mean you'll get to the right answer because the answer choice wording can be so tricky. To combat this, learn to recognize when these flaws are described as confusion. It will almost always follow this pattern: confuses (the thing it actually is) for/with (the thing that it isn't).

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