Question Type:
Weaken
Stimulus Breakdown:
Winter temps increased around the same time the northern cardinal started to appear in Nova Scotia. Therefore, the increase in temperature is the cause of the increase in bird population.
Answer Anticipation:
In general, the LSAT will weaken a correlation/causation argument by:
1) Providing an alternative cause
2) Providing a counterexample (cause without effect; effect without cause)
3) Bringing up reversed causality
The first is more common for earlier questions, so I'd head into the answers expecting an alternative cause. Also, the third possibility (increase in bird population caused an increase in temperature) makes no sense, so I wouldn't expect that.
Correct answer:
(A)
Answer choice analysis:
(A) Bingo. Alternative cause. The birds have feeders now, which caused them to increase in population. If you feed them, they will come.
(B) Out of scope. This answer choice is trying to get you to think that the increase in population is fake; the cardinal is easier to see, so it's easier to count. However, the survey was done both times on the same bird, so it would have been equally easy to see in 1980.
(C) Out of scope. This answer suggests something is causing an increase in bird populations, but it doesn't provide any alternative to the temperature increase.
(D) Too weak/unhelpful comparison. This answer is trying to get you to think that, since the nonmigratory bird (like the northern cardinal) populations fluctuated more than the migratory ones, the population numbers might be off. However, we just know that it fluctuated more, not that it fluctuated a lot. Since the comparison doesn't let us know if the numbers shifted enough to throw off the trend, this answer is wrong.
(E) Out of scope. If observations are showing an increase in population in spite of an increase in predation, then population really must have increased (to increase while also being hunted more). This answer, though, doesn't get at why it's happening.
Takeaway/Pattern: For early strengthen/weaken questions with a correlation/causation flaw, the correct answer will often deal with alternative causes.
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