PrepTest 152

Incorrect. The conclusion isn't based on there being a lack of evidence for the river not getting cleaner—it's based on the rankings. This answer describes an absence of evidence flaw, which isn't present here.

Incorrect. There's no ambiguity—the Sunvale Water Commission has some metric(s) they use to measure this, and it was applied in both years.

Incorrect. The basis for the ranking is the Sunvale Water Commission system. There's no need to get into details unless there's a suggestion that the system has issues.

Incorrect. The stimulus always compares all rivers to each other, so there's no part-to-whole jump.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Errors in Reasoning

Stimulus Summary:
Last year's report: Lalolah River was the most polluted of 15 rivers.
This year's report: Lalolah River was third-most polluted of 15 rivers.
Therefore, cleanup efforts must be working (i.e., the river is cleaner).

Answer Anticipation:
Lalolah's change in the rankings might be a result of the river getting cleaner. However, it might also be the result of other rivers getting worse. This answer uses relative premises (a ranking system) to justify a non-comparative conclusion (the Lalolah River is cleaner/cleanup efforts are working), which is flawed logic.

Answer Explanation:
This answer choice brings up the jump from relative premises (rankings) to the absolute conclusion (clean up efforts are working), so it's correct.

Key Takeaway:
As always, note comparative language in the stimulus—including rankings! These can generally be used to draw relative conclusions, but not absolute conclusions. Just think about it—just because you're shorter than a pro basketball player doesn't mean you're short.