PT77.S2.Q19 - a recent study examined

CrushLSATCrushLSAT Legacy Member
edited November 2016 in Logical Reasoning 150 karma
Hi All,

So I'm still struggling to identify exactly when certain arguments could be strengthened or weakened by the total number of samples (or any sort of number play for that matter) and when they cannot be. I remember seeing a few questions in the past where certain group was seeing a particular pattern or a phenomenon while the other group didn't and the discrepancy was due to some problems related to the size of the sample in one group (either their total number of participants were not counted properly, thereby inflating the trend) etc.

PT 77 Section 2 #19: A recent study examined the daytime and nighttime activity patterns of two populations of tree-dwelling lemurs - the first living in a rain forest, where tree canopy cover is consistent year0round, and the second living in a deciduous forest, where many trees lose their leaves during the winter months. Both groups of lemurs were found to be more nocturnal during winter months than they were the rest of the year. However, the winter increase in nocturnal activity was significantly more pronounced for the population living in the deciduous forest than it was for the population living in the forest.

For the question above, none of the answer choices really stood out for me initially and when I looked through them again, I noticed how the AC (D) was talking about the bird population in these forests are different, in fact, the lemur population in the rain forest is twice the size of the population in the deciduous forest... I thought that if that's the case, couldn't it be possible that the nocturnal activity looks more pronounced in the deciduous forest even though the two forests had the same number of birds that are both just as active at night? The correct answer turned out to be (B) which talked about the high-flying bird predators who hunt their prey during daylight...

So my question is, how are we supposed to know when these numbers actually come in play and exactly what the question means in this case - whether there are more % of these birds in each forest (in which case the population size matters) or it could be that the entire bird population is following a certain trend?


  • inactiveinactive Alum Member
    12637 karma
    Bumping so more people can see! Edited your title to conform with the 7Sage rules.
  • CrushLSATCrushLSAT Legacy Member
    150 karma
  • wildernesswilderness Alum Member
    edited November 2016 133 karma
    Okay. So in order to figure out why (D) is wrong, let's figure out why (B) is correct. This is a classic Resolve, Reconcile, Explain question type.

    We've got two populations of lemurs. One lives in the deciduous forest, where canopy disappears during the winter, and one lives in the rainforest, which maintains a thick canopy throughout the winter months.

    We're attempting to resolve the following discrepancy: why are the deciduous lemurs more nocturnally active than the rainforest lemurs?

    (A) is wrong because it talks about primary competitors for food for both populations being active in daylight. So what? We care about why deciduous lemurs are more active AT NIGHT than are rainforest lemurs. Scratch this out. This answer would explain why both are active at night, but not resolve the discrepancy we need it to.

    (B) is right. Let's say that there exists a predator for both lemur populations that uses its eyesight to catch lemurs during the daytime. Both lemur populations would want to hunt at night. Now, because of the canopy in the rainforest, more rainforest lemurs would be able to hunt in the morning because they'd be shielded from view from the predators. Thus, less have to hunt at night. The same can't be said for the deciduous lemurs. Since the canopy is gone (and therefore their natural protection from predators), more would have to hunt at night than in the deciduous forest.

    (C) is wrong. We're on the right track bc we're talking about predators. But it's the canopy difference (and consequently the difference in the forests) in the two lemur populations and its relation to why deciduous lemurs hunt more at night than do rainforest lemurs that we're attempting to reconcile. This is also wrong for the same reason (A) is. We care about why one group of lemurs is MORE ACTIVE at night than the other group. This would just explain why they're both active at night.

    (D) Your answer choice is incorrect. Think about it. The rainforest lemurs hunt LESS at night than do the deciduous lemurs. So even if it were the case that we see more lemurs hunting in the rainforest, this would mean that we'd see more rainforest lemurs at night than we see deciduous lemurs at night. If this is too strong, the question still arises that if (D) is correct, why don't we see more rainforest lemurs hunting at night than do deciduous lemurs if the rainforest lemur population is 2x that of the deciduous'? But that has the relationship completely backwards. Actually, we see more deciduous lemurs hunting at night. Also, you're making the assumption that "significantly more pronounced" in the stimulus means "we see more of them at X time." But this is ALSO wrong for the reasons I've just stated. It mixes the lemurs up.

    In other words the mistake I think you're making is this. The stimulus could very well be stating that we see 20% of rainforest lemurs hunting at night and 40% of deciduous lemurs hunting at night. Why is there a difference in percentage in relation to respective lemur populations? Even if it were the case that we see more literal lemurs hunting at night in the deciduous forest than the rainforest, the question still arises whether these numbers constitute a greater or lesser percentage of respective lemur populations... etc. We don't know whether we're talking about absolute number of lemurs or a discrepancy in the percentage of lemurs in each instance.

    (E) In J.Y.'s words, who the fuck cares about whether rain forest lemurs are eating plants and insects or what the fuck.
  • CrushLSATCrushLSAT Legacy Member
    150 karma
    @wilderness Hey, thank you so much for your help again! So in this case, you are saying whether there is a significant difference between the population size of these birds is irrelevant because even if that was the case, it still doesn't explain the fact that why birds in the deciduous forest was more active, correct? I think I was making an error in thinking that by canceling a discrepancy between these two bird populations by providing some other evidence (i.e. we are not comparing apples to apples bc of significantly different sample size difference etc) would resolve the discrepancy but that wasn't really what the question was asking me to do after all :). The approach should be to really "explain" the difference not somehow say that there is no difference!
  • wildernesswilderness Alum Member
    edited November 2016 133 karma
    Yes, exactly. It's worth mentioning that lemurs aren't birds, also.

    What I'm saying is this. The answer choice (D) says:

    (1) There are 2x rainforest lemurs than deciduous lemurs

    We're asked to solve why

    (2) We see more deciduous lemurs at night than we see rainforest lemurs

    So... even under your line of reasoning, if it were simply the case that because there are more of one type of lemur than another... it doesn't account for the fact that answer choice (D) says that there are 2x RAINFOREST LEMURS than deciduous lemurs. But we're not looking to explain why there are more rainforest lemurs... we're asked to resolve why there are more deciduous lemurs at night.

    The second point is this. We don't know off the top of our head whether or not the scientists are even accounting for total number of lemurs. So like, let's say that we simply see more of one type of lemur at night than the other. How do you know that the scientists aren't stating that they're seeing, for example:

    (3) 20% of 200 rainforest lemurs = 40 rainforest lemurs at night
    (4) 40% of 100 deciduous lemurs = 40 deciduous lemurs at night

    (Here, we see a greater % of deciduous lemurs out at night even despite the fact that there are 2x as many rainforest lemurs. We're asked to figure out the percentage, I think, rather than the total number. As you see, changing the total number of lemurs (200 rainforest v. 100 deciduous) doesn't really account for anything or resolve anything if the % are as followed).

    ??? In this instance, the rainforest lemur population is 2x that of the deciduous lemurs. We don't know whether we're talking about simply seeing more of a percentage of deciduous lemurs or more of a total number of deciduous lemurs. Neither the answer choice nor the stimulus indicate either way. But you're making an assumption that this statement means a specific thing, and you want to be wary of introducing assumptions that have no basis in ur answer choices.
  • twssmithtwssmith Alum
    5120 karma
    @wilderness Great explanation!
    @CrushLSAT said:
    I'm still struggling to identify exactly when certain arguments could be strengthened or weakened
    For a great global view of Strengthen/Weaken strategies, check out this webinar:)
  • CrushLSATCrushLSAT Legacy Member
    150 karma
    @wilderness And all this time I thought they were birds after reading AC (B) lol I just googled to check out what real lemurs look like lol Thanks for the thorough explanation - really appreciate it :D
  • CrushLSATCrushLSAT Legacy Member
    150 karma
    @twssmith Thanks!! I actually watched this webinar awhile back but it didn't really make much sense to me. I rewatched bits of it today and it seems to resonate more with me after doing more questions which is good lol
  • twssmithtwssmith Alum
    5120 karma
    @CrushLSAT Lemurs are cute aren't they:)
    Hey, I attended that webinar and the BR call that spurred the webinar - I still re-watch it as I gain more understanding as I progress thru PT phase!
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