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Course: LSAT > Unit 1
Lesson 8: Logical Reasoning – Worked examples- Identify the conclusion | Worked example
- Identify an entailment | Worked example
- Strongly supported inferences | Worked example
- Working with disputes | Worked example
- Identify the technique | Worked example
- Identify the role | Worked example
- Identify the principle | Worked example
- Match the structure | Worked example
- Match principles | Worked example
- Identify a flaw | Worked example
- Match flaws | Worked example
- Necessary assumptions | Worked example
- Sufficient assumptions | Worked example
- Strengthen | Worked example
- Weaken | Worked example
- Helpful to know | Worked example
- Explain | Worked example
- Resolve a conflict | Worked example
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Necessary assumptions | Worked example
Watch a demonstration of one way to approach necessary assumption questions. Created by Sal Khan.
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- Can the video be rescaled to show all the solutions right away? The final (and correct) response is hidden for most of the video, thereby making it impossible to pause and the do the question on your own.(44 votes)
- why cant we see the questions and predict sal's response. I did not find this exercise challenging.(10 votes)
- Nobody has time to diagram LR this much in a real test and it shouldn't have taken this much work to see which choice is correct. Please stop misleading the students...(9 votes)
- ANSWERS
(A) Of the armadillos living int he area of the tagging site last spring, few were able to avoid being tagged by the researcher.
(B) Most of the armadillos tagged the previous spring were not recaptured during the subsequent fall.
(C) Predators did not kill any of the armadillos that had been tagged the previous spring.
(D) The tags identifying the armadillos cannot be removed by the armadillos, either by accident or deliberately.
(E) A large majority of the recaptured armadillos did not move to a new territory in the intervening summer and then move back to the old territory by the fall.(4 votes) - The question that I have for answer choice A is that if we suppose, that the researcher only captured 1 armadillo and it didn't move much, we could not conclude that armadillo do not move rapidly. Answer choice A makes the sampling more representative.(3 votes)
- For those seeking to answer this question, just know that there are five answer choices, and the last one is hidden due to scaling issues in the video frame. Please be advised.(1 vote)
Video transcript
- [Instructor] So a
researcher is saying this fall I returned to a research site
to recover the armadillos I had tagged there the previous spring. Let me just write this. So previous spring. Previous, previous spring. Then there is this fall, this fall. So we're moving in time
and he returns to a site to recover armadillos. So let's say that this is a broader region and he's returning to a
site, so this is the site right over here. And he returns to that
site, so I'm drawing the broader region and I
have this site over here. So this fall I returned to
a research site to recover the armadillos I had
tagged the previous spring. So let's say here are the
armadillos that he tagged the previous spring. Since a large majority of
the armadillos I recaptured were found within a few
hundred yards of the location of their tagging last spring. So he's recapturing them so these are ones that he tagged before. He's saying a large
majority were found within a few hundred yards of the
location of their tagging last spring. He concludes that armadillos
do not move rapidly into new territories. I concluded that armadillos
do not move rapidly into new territories. Now before I even look at the choices, and we're supposed to answer the question, which of the following
is an assumption required by the researchers argument? One question that immediately
jumps in my brain, well he's assuming that
they didn't go some place in between. Maybe they went, you
know, maybe they went here during the summer,
which is quite far away, and then by fall they came back. So there's some type
of migratory behavior. He's assuming that in order
to conclude that armadillos so not move rapidly into new territories because they might have
moved super fast into another territory and then come back. So let's see if any of
these choices speak to that. Of the armadillos living in
the area of the tagging site last spring, few were
able to avoid being tagged by the researcher. Well no, his assumption
isn't based on the proportion of armadillos, of all the
armadillos he was able to tag. He's just saying that of
the ones I'm recapturing, a lot of them seem to
be near the same area so it doesn't seem to be
a key assumption required. Most of the armadillos
tagged the previous spring were not recaptured during
the subsequent fall. No, that's not a key
assumption that he's making. In fact, that would undermine
his position if he's only able to get a very small fraction. Most of the armadillos
tagged the previous spring were not recaptured the subsequent fall. That would actually give
a problem to his argument. Predators did not kill
any of the armadillos that had been tagged the previous spring. No, he's not saying that he
recaptured all the armadillos or he needs to recapture
all the armadillos. It's possible that predators
killed a few of them but he's recapturing, he's
saying that of the ones that he recaptured, that
the majority were within a few hundred yards of this same location. So it doesn't mean that he
has to get all of them back, that we can't, you know,
all of them have to be alive from one year to the next. It's just most of them have to be around. D: The tags identifying the
armadillos cannot be removed by the armadillos, either
by accident or deliberately. Now once again, this is very close to C. He's not saying that he
has to, that all the tags have to be there. As he said, he's just saying,
the majority of the armadillos he recaptured, so he is
assuming he had to recapture a good chunk of them, but not all of them. So even if some of the tags
get removed or some predators kill some of the armadillos,
doesn't seem like that big of a deal. Now let's go to the last
choice, which is hopefully the answer since I ruled
out the first four. A large majority of the
recaptured armadillos did not move to a new territory in
the intervening summer and then move back to the
old territory by the fall. Well this is actually almost
word for word what I was having trouble with before. He's assuming, or she is assuming, the researcher is assuming
that they didn't go, that the large majority did
not move to a new territory and then come back in
the intervening summer. So this for is sure the
key assumption required by the researchers argument.