If you'd like, feel free to send me a personal message with a question that has caused you some difficulty, and we can try and work through the flaws in reasoning.
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Messages - ssilver0210
« on: April 18, 2010, 10:46:49 PM »
We are told in the question, that in this world you are either rich or poor, and that all poor farmers are honest, so that all rich farmers must be dishonest. The flaw here is that even if it's true that in the world you are either rich or poor, and that all poor farmers are honest, it still might be true that some or all rich farmers are also honest. If choice A, however, is taken as true, so that every honest farmer is poor, then it's no longer a possibility that some or all rich farmers are honest (honesty requires being poor), and the conclusion of the passage can be properly drawn.
The sentence later in the passage states that parents who wish to provide a good musical education for their children need to ensure that their children receive formal instruction.
We know from the passage that formal instruction is often, but not always, a part of a good musical education. This means that there are times when formal instruction is not a part of a good musical education. If that's the case, though, then a conclusion stating that parents need to provide their children with formal instruction in order to ensure a good musical education, is too strong a conclusion, because in some cases (those in which formal instruction is not a part of good musical education), parents need not provide such formal instruction in order to ensure a good musical education.
« on: November 25, 2009, 12:19:23 PM »
CHOICE E: Even if many of the earliest sophisticated tools did not require the user to stand upright, it's still quite possible that they had the ability to stand upright before developing these tools. We are looking for an answer choice that makes it likely that prehistoric humans developed tools before they had the ability to stand upright.
CHOICE B: Advanced hunting weapons have been found among prehistoric humans who did not stand upright. If this were true, then these humans who did not stand upright were able to develop sophisticated tools. In other words they had the ability to develop tools, even though they were known to have not stood up. This contradicts the conclusion of the passage which states that humans stood up before developing tools, and in that sense, it most weakens the argument.
You're correct, the wrong answer was too vague with the words "other organisms," where as the correct answer directly addressed Plankton.
Pay close attention to what the argument is stating. It's stating that because various brands of motor oils, when tested, did equally well in retarding engine wear, it's best to buy the cheaper brands.
Choice B simply tells us that tests, other than the one conducted, can also reliably gauge the quality of motor oil. The problem with this argument, though, is with the specific test stated in the argument. The author failed to consider the possibility that even though the motor oils all performed equally well when tested in that one specific area (for engine wear), it's possible that more expensive oils might have benefits that the cheaper ones do not. So he was not justified in concluding that people should buy cheaper oils simply because all of the oils performed equally well in that one specific area.
In your hypothetical you added the part about "if tests prove that cheaper motor oils are the best buys." Choice B only states that other tests are available--the simple fact that other tests are out there, and available, doesn't weaken the argument to the extent that the other choice does.
Take this argument, for example:
Two quarterbacks were tested by two NFL teams to determine which player to pick for their team. After testing both players' ability to throw long distances, both teams concluded that the ability of the players in this regard was equal, so that the better pick would be the player who demanded less money.
Similar to the motor oil example, the teams would not have been justified in making that determination, because it's quite possible that one of the players had many skills that the other player did not have, even though they both performed equally well in that one area of throwing the ball long distances. A wider range of skills should have been tested to determine which player to pick. If they each performed equally well in all areas, then a conclusion to pick the cheaper player is more justified.
The first one:
The conclusion of the passage states that if an amateur astronomer is buying a telescope for planetary observation, then he/she should buy the exodus. Image quality of the Exodus telescope was stated to support this conclusion. If it were true, as answer choice C says, that many serious amateur astronomers have no intention of buying a telescope for astronomical observation, that would not weaken the conclusion of the argument, because the conclusion merely states that amateur astronomers who intend to observe the planets should buy the exodus due to its superior image quality. Those who do not intend to observe the planets are beyond the scope of the argument.
On the other hand, let's now assume that it's true that image quality is only one of several factors that taken together should determine the choice of telescope for amateur astronomers, as choice B says. If that were true, then it weakens the conclusion that an amateur astronomer should purchase the Exodus telescope simply because it has better image quality. In other words, it's not enough to know about image quality when determining which telescope to buy, other factors must be included along with it. So, if choice B were true, the conclusion of the passage is seriously weakened.
The second one:
The argument said the various brands of motor oil were tested to determine which oil is best for a car. All brands did equally well in protecting the engine from wear. Therefore, according to the passage, people should buy the cheaper brand of oil since all brands functioned equally well.
But what if it were true that oil has benefits other than protecting the engine from wear. (choice e) If that were true then it's possible that more expensive oil might be more beneficial for those benefits, even though all brands of oil functioned equally well in protecting the engine from wear. In that case, one might want to purchase the more expensive oil for the additional benefits. So, the conclusion, that one should purchase the cheaper oil is seriously weakened if it's true that motor oil has benefits other than protection from engine wear.
Choice B tells us that there are tests other than the one conducted which could reliably test the quality of motor oil. This does not weaken the argument, however, because it does not state that the test conducted in the study was unreliable, it simply states that other reliable tests might also be available.
Think of it this way:
What if a national economy could prosper even if significant influence on that economy had not been examined by the nation's government economists. In other words, prosperity in a national economy was not dependent upon the economists examining every significant influence. (the negation of answer choice A)
If that were true, then we could no longer conclude that a nation's economy certainly will not prosper when that nation's economists fail to look beyond national borders to examine all potential significant influences. It's possible that the economy will still prosper even though influence beyond national borders has not been examined.
But we are told in the passage that in order for a national economy to prosper, the economists of that nation must look beyond national borders to examine all influences. (the conclusion of the passage).
So, when you take the negation of answer choice "A", the conclusion of the passage is no longer valid. Because of that, we can say that answer choice A must be assumed for the conclusion of the passage to follow logically.
Assume that it were true that successful strategies for overcoming adolescent loneliness sometimes intensifies that loneliness. (the negation of choice B).
We're told in the passage that there is a strategy for overcoming loneliness, but that strategy can sometimes actually intensify the loneliness. Because of that fact, we're told that strategy is not a successful one. (the conclusion of the passage)
But if the negation of choice B is true; namely, that successful strategies for overcoming loneliness can intensify the loneliness, then the conclusion of the passage (that the strategy is unsuccessful simply because it intensifies loneliness) is no longer true.
In order for the conclusion of the passage to be true, it must be true that no successful strategy for overcoming adolescent loneliness never intensifies the loneliness. Because that must be true, it is an assumption on which the argument depends.