PT151 S3 Q13 ExplanationA new screening test

Answer choices, explained

1. A

   Correct90% picked this

   It confuses the claim that a subject will test positive when the syndrome is present with the claim that any subject who

   Why this is right

   This describes the Necessary vs. Sufficient error by comparing the conditional the author actually gave us with the conditional the author would have needed to give us in order to reach her conclusion. She gave us, "when syndrome is present, test is positive" Q is present → test is positive She wanted a claim that says "any subject who tests positive has the syndrome" test is positive → Q is present After all, she tells us that Justine has tested positive. That doesn't trigger anything in the first rule, the one the author presented. Another way to say all this is, "the author confuses a rule where testing positive is the Necessary condition with a rule where testing positive is the Sufficient condition". But it triggers the 2nd rule and would allow the author to reach her conclusion

   Skill tested: Flaw · how this choice captures the argument's function is the move to repeat next time.

   90%
2. B

   Out of Scope: general accuracy claim3% picked this

   It makes a general claim regarding the accuracy of the test for syndrome Q without providing adequate scientific

   There is no explicit claim made regarding the accuracy of the test, so this answer is just descriptively false. The author is implicitly accepting the accuracy of the test, that's true. She does say that "research has shown ..." that the test yields no false negatives. So there also kind of is some scientific justification to her trust the accuracy of "if you have syndrome, then test will say positive".

   3%
3. C

   Scrambled Ideas4% picked this

   It fails to adequately distinguish between a person’s not having syndrome Q and that person’s not testing

   This has an overall form that could work if we inserted the right ideas into it: This argument failed to distinguish between testing positive for Q and actually having syndrome Q (i.e. it failed to appreciate the possibility of false positives -- a positive test doesn't mean for sure you have it). This answer is saying the author failed to appreciate the possibility of false negatives --- that you might not test positive but still actually have syndrome Q.

   4%
4. D

   Out of Scope: group vs. individual2% picked this

   It confuses a claim about the accuracy of a test for syndrome Q in an arbitrary group of individuals with a similar claim about

   There's no distinction anywhere in this argument between the test being accurate for groups but not for individuals, or vice versa. This answer seems to be teasing some sort of Sampling or Part vs. Whole issue that wasn't present in the argument. Like, "even though that was true for this group, it won't necessarily be true for Justine". We can't match that up with this argument.

   2%
5. E

   Out of Scope: no reliable results1% picked this

   It confuses the test’s having no reliable results for the presence of syndrome Q with its having no reliable results for

   When a Flaw answer choice is saying the author confused X with Y, it's saying that X is what was talked about in the evidence but Y is what the author was apparently thinking in drawing her conclusion. Neither the evidence nor the conclusion talked about "a test having no reliable results".

   1%