PrepTest 114, Section 1, Question 4
An anthropologist hypothesized that a certain medicinal powder(63 more words not shown)
Which one of the following,(7 more words not shown)
- AThe anthropologist had(14 more words not shown)
- BThe activity level(15 more words not shown)
- CWhen it is(9 more words not shown)
- DA fresh batch(14 more words not shown)
- EThe type of(11 more words not shown)
Reading the argument
Why would acid make the negative result untrustworthy?
I understand the initial suspicion. The anthropologist expected to find toxin T and didn't report the test that failed to find it. But we shouldn't assume that a negative result proves the toxin absent, or that we already know why she withheld the result. Her explanation is that the test was invalid because it used an acidic solution.
What we’re looking for
That explanation needs a connection. If acid interferes with the test, the objection could make sense. If acid makes no difference, merely mentioning it doesn't explain anything. For a strengthener, I'd predict evidence that putting toxin T in acid prevents the test from detecting it.
Working the answers
- A
This gives the anthropologist a reason for the original hypothesis. It doesn't show that this particular test was invalid. A person can have evidence for expecting a result and still conduct a valid test that goes the other way. We need support for the acid-based objection, not just for the expectation she began with.
- B
We aren't told that this powder had been stored for a long time. More importantly, the anthropologist's explanation concerns the acidic solution, not prolonged storage. B offers a possible issue under a condition we haven't been given; it doesn't connect the stated testing condition to invalid results.
- CCorrect
Now the acid matters. If toxin T becomes undetectable in an acidic solution, a negative result from this test wouldn't show that the original powder lacked it. The testing conditions could prevent detection even when the toxin was present.
That supports the anthropologist's claim that this result is invalid as evidence against her hypothesis. 'Undetectable' doesn't mean the toxin has been destroyed, and C doesn't settle every question about whether withholding results was appropriate. It supports the specific reason she gives for distrusting this test.
- D
Having another batch available means another analysis was possible. It doesn't tell us whether the completed analysis was valid or whether acid affected it. Asking why she didn't retest is a different question from establishing the problem she claims occurred.
- E
Missing very small amounts doesn't address a hypothesis that the powder contained a significant amount. Even if a trace quantity could escape detection, that wouldn't establish the claimed problem with testing in acid. This answer gives a limit on the analysis without the connection her counterargument needs.
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