Logical reasoning PrepTest 125 · Section 2 · Question 14

Incorrect. This answer doesn't tie speeding tickets into the actual number of people speeding, the number of cops on speeding duty, or the amount over the speed limit people were driving, so it doesn't provide enough information for us to know if it affects the argument.

Incorrect. This answer eliminates an alternative cause—more cops patrolling, thus resulting in people driving better—and thus strengthens the argument.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Weaken

Stimulus Summary:
A reduction in serious traffic accidents was seen after the speed limit was reduced, so the speed limit reduction caused the decrease in serious accidents.

Answer Anticipation:
A Weaken question with a causal conclusion ("led to")? That means there's almost certainly a correlation/causation flaw in the stimulus!

Looking at the premises, we see that the conclusion is based on a correlation—the decline in serious accidents started after the speed limit was reduced. Since this Weaken question has a correlation/causation flaw, we should look for the normal correct answers in this pattern:
(1) ID an alternative cause (maybe the speed limit decrease was part of a package of changes meant to address the number of serious accidents, and one of those other changes caused the decrease)
(2) Counterexamples (maybe the next town over didn't decrease their speed limit and saw the same decrease in serious accidents; or another town decreased the speed limit and didn't see such a decline)
(3) Reversed causality (this doesn't work here since the speed limit drop happened before the decline)

There's one more thing we need to consider that comes from another common issue in a question like this—the definition of serious accident. Whenever the LSAT defines a category, there's a chance that a correct answer (or trap answer) will highlight that the definition changed, and thus the comparison is off. For example, here, if the definition of "serious accident" used to include only accidents with death, then the expectation would be that the number of accidents would increase under the new definition, which is broader.

In general, you want to determine if the new definition is broader or narrower than the initial definition, and then determine if that means the argument is stronger or weaker. Here, if the definition is narrowed, then the reported number of serious accidents would be expected to go down, so the argument would be weakened. If the definition is broader, then the reported number of serious accidents would be expected to go up, so the fact it went down strengthens the argument.

Answer Explanation:
This answer proposes an alternative cause to the speed limit—there are fewer serious accidents because there are fewer people on the road. Since it proposes an alternative cause, it weakens the argument.

Key Takeaway:
When the LSAT defines a category, there's a good chance that at least one answer will address that definition. Determine whether the change in definition narrows or broadens that definition, and how that change affects the argument.

Incorrect. In general, answers that keep other factors stable will serve to strengthen correlation/causation flaws by suggesting that alternative causes aren't present, so we can eliminate this answer.

Incorrect. Here's the answer that addresses a change in the definition, as we anticipated! However, the new definition is broader (old—just extended hospital stay; new—death or any hospital stay) than the old one, so the accident rate would be expected to go up under it, and the fact that it went down suggested something had a positive impact on it, thus strengthening the argument.