June 2007 LSAT Question Explanations June 2007 - Sec 2 - LR...

June 2007 - Sec 2 - LR - Q5

Video Transcript:

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Question 5 - Scientists:
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Earth's average annual temperature has increased by about 0.5 degrees Celsius over the last century. This warming is
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primarily the result of the buildup of minor gases in the atmosphere, blocking
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the outward flow of heat from the planet. Alright so argument or facts? We
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have an argument. The scientist is trying to explain something to us and his
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conclusion is that this warming is primarily the result of the buildup of
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minor gasses in the atmosphere blocking the outward flow of heat from the planet.
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So that's the scientist's conclusion or hypothesis. You notice this is a
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cause-and-effect argument. There is something that this scientist is trying
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to explain to us. There is an observed effect. And what is that observed effect? It
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is that the Earth's average annual temperature has increased by about 0.5 degrees Celsius over the last century.
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What is the scientist's proposed explanation for this observed effect of
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the Earth's warming? It is the buildup of minor gases. So he's proposed cause is
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this buildup of minor gases that are blocking the outward flow of heat from the
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planet. So now that we have a clear understanding of this passage let's
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proceed to the questions stem. Which of the following if true would count as evidence against the
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scientist's explanation of the Earth's warming. You notice 'evidence against'. This is a
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weakening question.
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Asking us to weaken this scientist's explanation of the earth's warming. So let's take a look at (A).
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Only some of the minor gasses whose presence in the atmosphere
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allegedly resulted in the phenomenon described by the scientist were produced by
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industrial pollution.
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OK, that is completely irrelivant
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This argument is not about where these minor gases are coming from.
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So (A) would be eliminated. Moving to (B). Most of the warming occurred before 1940 while most of
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the buildup of minor gases in the atmosphere occurred after 1940. So what (B) is telling us
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on this timeline that we have
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1940
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Prior to 1940 had most of the warming. After nineteen forty we had most of the minor
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gas buildup. So does that weaken this
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arguement? And it does because it shows that our observed effect, the warming, was
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present without this proposed cause of the buildup of minor gases because again
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most of the warming occurred before the nineteen forties while most of the
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buildup of minor gases occurred
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after the nineteen forties. So (B) does weaken by showing effect without cause. And
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we know that's one of the three ways to weaken a cause-and-effect argument. So (B) would be the correct
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answer. But again let's make sure because (C) is a very popular answer choice among
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students. (C) tells us over the last century earth received slightly more
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solar radiation in certain years than it did in others. And a lot of students pick (C)
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because the test makers are trying to trick you into thinking that (C) is an
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alternate cause. But is it really an alternate cause? We know alternate causes are
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another way to weaken it cause-and-effect argument. But if you noticed (C) doesn't
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tell us that over the last century earth received slightly more solar radiation
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than the previous century. It says in certain years than it did in other
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years. So you notice it is not an alternate cause because (C) is not
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comparing this past century to the century before it it is comparing certain
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years with in this last century with other years within this last century. So it
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is not an alternate cause because our observed effect was that the earth's average annual
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temperature
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the average
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increased. So even though we had slightly more radiation in certain years than in others
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still on average there was a temperature increase of 0.5 degrees Celsius. So, (C) would be eliminated.
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It's a trap answer. They're trying to trick you into thinking that that is an
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alternate cause. And it said over the last century earth received slightly more
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solar radiation than it did in the previous century that would be an
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alternate cause and it would have been the correct answer. Checking (D). Volcanic
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dust and other particles in the atmosphere reflect much of the Sun's
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radiation back into space before it can reach earth's surface. Ok great. So what?
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That does nothing to our argument here. So (D) would be out. (E) The accumulation of minor
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gases in the atmosphere has been greater over the last century than any other
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time in history. And you notice (E) actually strengthens this argument by
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showing that this cause has been most pronounced in this past century than at
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any other time in earth's history. So clearly strengthens the argument. But again we
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are trying to weaken. So (E) would be eliminated. Again remember that (C) was not
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an alternate cause. Trap answer choice. (B) again the correct answer because it
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shows effect without cause.