Logical reasoning PrepTest 124 · Section 1 · Question 9

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen with Necessary Premise

Stimulus Summary:
Nesting female leatherback turtle population is down more than _ over the past 15 years
Species whose population drops more than _ in 15 years → Grave danger of extinction
Therefore - Leatherback turtle is in grave danger of extinction

Answer Anticipation:
This argument falls into a common pattern on the LSAT—it presents a principle/conditional and then attempts to apply it to a specific situation. When this is the case, the flaw is usually that the argument fails to fully establish the presence of the sufficient condition.

Here, the sufficient condition of the conditional is that a species' population must decline at least _ over 15 years. A quick reading of the information about the leatherback turtle population may make it seem as if it has established this, but there's an important difference—the population statistic established is just about the nesting female leatherback turtle population. If the male leatherback turtle population hasn't declined as much or more than _, then the argument falls apart. Same with the non-nesting female turtle population.

Note that the argument needs to establish enough about the overall population being in decline to trigger the sufficient condition here. We don't know the sex mix of the leatherback turtle population, so anything that talks just about the number of the male leatherback turtle population won't help us here, as that would see us committing a Percent vs. Amount flaw in picking our answer.

Answer Explanation:
This answer establishes that the _ decline in the female population is the same as the decline in the overall population. Thus, the overall population has declined by at least _ in the past 15 years, triggering the conditional. If the overall population hasn't declined by a proportional amount, the conditional doesn't apply and the argument falls apart.

Key Takeaway:
When an argument attempts to apply a conditional to a specific case, it will generally be flawed in that it fails to fully establish the sufficient condition. When that's the case, the correct answer will address that gap.

Incorrect. The conclusion is about what is currently the case, so it doesn't rely on what could be true in the future.

Incorrect. First, this answer is about the number of turtles, not the proportion of the population that has disappeared. Second, it doesn't establish if the starting point 15 years ago was the same—if there have always been significantly fewer male leatherback turtles, then there being equal numbers now doesn't evince a decline in the male population.

Incorrect. It's unclear if "nesting" leatherback turtles are all wild or not, so it's unclear how a lack of turtles in captivity has anything to do with the argument.

Incorrect. This answer is way too strong and out of scope to be necessary for an argument about the population, not about whether something needs to be done about it.