Logical reasoning PrepTest 118 · Section 1 · Question 20

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen with Sufficient Premise

Stimulus Summary:
There's some connection between meteorite impacts and mass extinctions, but it's not consistent, so there's no consistent causal link between meteorite impacts and extinction.

Answer Anticipation:
Interestingly enough, this argument uses a lack of consistent correlations to prove that there's a lack of consistent causation. In other words, it assumes that if two things aren't always correlated, then they aren't consistently causally related. However, that's a jump as much as assuming that a correlation proves causation! A causal link can exist without the correlation being consistent—just think about, for instance, smoking and lung cancer, where not everyone who smokes ends up with the disease.

The correct answer will have to make that connection—if two things aren't consistently correlated, then they can't be consistently causally related.

Answer Explanation:
This answer is the contrapositive of the anticipation we had. We know from the stimulus that all major meteor impacts have not been followed by mass extinctions, so this answer choice therefore guarantees (again, contrapositive) that there isn't a consistent causal link between meteorite impacts and mass extinctions—our conclusion. Since it justifies the conclusion, this answer is correct.

Key Takeaway:
An interesting twist on correlation/causation! Even if that threw you a bit for a loop, you should still have focused on those elements, as we've seen time and again how important they are to the LSAT.

Incorrect. The stimulus states that the geological record contains "some" hints of major meteor impacts preceding mass extinctions, so it's possible many mass extinctions have followed major meteor impacts. The information is the stimulus—where each correlation is phrased as a "many" statement—is too weak to rule that out, so this answer doesn't necessarily apply to the geological record.

Incorrect. This answer is trying to establish that the geologic record is complete, and that we're not "missing" a meteor impact that preceded a mass extinction. However, that doesn't establish a connection between correlations and causation—it just rules otu one potential issue with the argument, and is therefore closer to a necessary assumption than a sufficient one.

Incorrect. This answer reverses the logic of the stimulus by starting with, "If there is no consistent causal link . . . " which is what the argument is trying to conclude.

Incorrect. The conclusion is that there isn't a consistent causal link, so this answer stating that there could be a link even without perfect correlation undermines the argument, which is the opposite of what we're looking for.