Logical ReasoningDifficulty: Hard

PT150 S3 Q15 Explanation

Carrillo: Using the number

A free, expert breakdown of this official LSAT Logical Reasoning question.

TopicsAgree/Disagree

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Stimulus

Carrillo: Using the number of existing primate species, along with measures of the genetic diversity among these primates and among the extinct primate species, our statistical model strongly supports the developed around 81.5 million years ago.

Olson: Given that the oldest primate fossils discovered so far date back only 55 million years, your estimate of how long primate on is sheer speculation.

What this question is testing

Agree/Disagree

Your task

Break the argument into its conclusion and evidence, then do exactly what the question stem asks with that structure.

Common trap

Answers that sound relevant to the topic but don't connect to the argument's actual reasoning.

Winning move

Predict what a right answer must do, then test each choice against the conclusion-evidence gap.

Reading along? Open the full official question in LawHub — we show a fragment here and keep the reasoning in our own words.

The question
15.

The dialogue provides the most support for the claim that Carrillo and Olson

Answer choices

  1. Unsupported Disagree Position23% picked this

    primates have been around for more than 55

    We can't support the Disagree position, "Primates have not been around for more than 55 million years". The 2nd speaker isn't saying that 55 million years is definitely the beginning of primates. He's just saying that it's sheer speculation to think it's 81.5 million years ago. In other words, Olson would say, "I don't know how long primates have been around. It's at least 55 million years, since we have fossils that old, but I do not trust this crazy-different number your statistical model came up with."

  2. Correct69% picked this

    Carrillo's statistical model is a reliable way of dating the first appearance

    Why this is right

    The notion of whether or not this model is a reliable way speaks to the mismatch we located between "strongly supports" and "sheer speculation". We can infer that Carrillo would agree because the thinks this model strongly supports a conclusion about the first primates. And we can infer Olson would disagree since he says, "your estimate is sheer speculation, given a completely different number we get from a more reliable source of information".

    Skill tested: Agree/Disagree · how this choice captures the argument's function is the move to repeat next time.

  3. Both Positions Unsupported3% picked this

    the available sample of primate fossils is representative of the variety of primate species

    We can't infer whether either person thinks that the available sample is representative of the variety that have existed, since neither person speaks to that concept. Carrillo would be the closer one to believing this, but he doesn't need the available sample to be representative for his model to provide strong support. As long as he knows how to weight the un-representativeness of his sample, he can still have an accurate model. (Pollsters can talk to 2000 people and realize that certain factions of the population are under-represented in their sample, but then they compensate for this by making those data points count for more than just one data point.)

  4. Unsupported Disagree Position4% picked this

    the dating of the primate fossils that Olson cites

    Olson would probably agree to this, but can we derive that Carrillo would say "those fossils you're referring to have been incorrectly dated at 55 million years old"? Definitely not. First of all Carrillo never talks about those fossils at all. Secondly, he's only talking about when the first primate developed, not whether the carbon dating on existing fossils was done properly.

  5. Unsupported Agree Position2% picked this

    fossils of the first primate species that developed have

    We wouldn't be able to derive this from either party's statements. Carrillo, if he trusts his 81 million year estimate and knows that the fossils are 55 million years, might think "those 55 million year old fossils aren't the fossils of the first primate species". But would Olson say, 'yes they are. The oldest primate fossils discovered so far are fossils of the first primate species'? We have no idea, but it seems like by saying "so far", Olson is allowing for the possibility that we'll discover even older fossils, so he'd likely be receptive to the possibility that these 55 million year old fossils we have aren't from the very first primate species.

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