Quincy: I am skeptical that the association between the lights and the earthquakes is anything more than a coincidence. The theory that ground stresses related to earthquakes can cause any kind of lightning is extremely speculative.
Summarize Argument: Counter-Position
Quincy concludes that Phoebe’s explanation of strange glowing lights as earthquake-induced is unconvincing. This is supported by the claim that the mechanism Phoebe proposes for her explanation—ball lightning forming as a result of ground stresses—is “extremely speculative.”
Describe Method of Reasoning
Quincy counters Phoebe’s argument by casting doubt on the mechanism she proposes to explain a phenomenon. By pointing out that earthquake-related ground stresses are not known to cause any kind of lightning, Quincy undermines Phoebe’s conclusion that the strange lights were “almost certainly” caused by earthquakes.
A
takes a correlation to be a causal relation
Quincy doesn’t say that any causal relationship exists based on a correlation. In fact, he’s arguing against Phoebe’s claim that a causal relationship exists.
B
challenges the accuracy of the data about sightings that Phoebe takes for granted
Quincy doesn’t challenge the accuracy of any of Phoebe’s data about the sightings. He accepts that the sightings have happened; he only doubts her explanation for the phenomenon.
C
criticizes Phoebe’s explanation as unsubstantiated
Quincy criticizes Phoebe’s explanation of strange glowing lights being ball lightning caused by earthquakes, because it is founded on a speculative—meaning unsubstantiated—theory about the potential of earthquakes to cause lightning.
D
offers an explanation of the glowing lights different from Phoebe’s
Quincy doesn’t offer any alternative explanation of the glowing lights, only casts doubt on the plausibility of Phoebe’s explanation.
E
accuses Phoebe of introducing irrelevant information
Quincy doesn’t claim that Phoebe has introduce any irrelevant information, only that she has interpreted the information in a questionable way based on speculative theories.
Summary
The stimulus can be diagrammed as follows:
Notable Valid Inferences
Most speed readers have above-average intelligence.
A
Some people can speed-read, and are able to fully concentrate, but are of below-average intelligence.
This must be false. We know that all people who are able to fully concentrate are of above-average intelligence.
B
All people who can speed-read are of above-average intelligence.
This could be true. We know for sure that most speed readers are of above-average intelligence; it could still be true that all are of above average intelligence.
C
Many people of above-average intelligence are unable to fully concentrate.
This could be true. We know that all people who can fully concentrate are of above-average intelligence, but this doesn’t mean that everyone of above-average intelligence can fully concentrate.
D
Some people with little ability to concentrate are of below-average intelligence, but can speed-read.
This could be true. If someone of is below-average intelligence, then they can’t fully concentrate. It could totally be the case that this person has the ability to speed read.
E
All people who can speed-read are able to concentrate to some extent.
This could be true. The only factor related to concentration discussed in the stimulus is “full concentration;” it could be the case that all people who can speed read can concentrate at least a little bit.
A
a nation that fails to invest in its infrastructure need not experience any resulting decline in its standard of living
The author’s conclusion is about a nation experiencing a rise in its standard of living as a result of investment in its infrastructure, not a decline in standard of living as a result of failing to invest in infrastructure.
B
many nations are unable to make the needed investments in infrastructure
Like (C) and (E) this may be true, but it doesn’t impact the author’s argument. Even if many nations can’t invest in infrastructure, it doesn’t affect the conclusion that such investments are necessary for a higher standard of living.
C
the rise in a nation’s standard of living that is prompted by investment in its infrastructure may take a long time to occur
Like (B) and (E) this may be true, but it doesn’t impact the argument. Even if the rise in standard of living takes a long time, it doesn’t affect the conclusion that investments in infrastructure are necessary for it to occur. The author even notes that it happens “over time.”
D
a rise in a nation’s standard of living need not be the result of major investments in its infrastructure
The author mistakenly assumes that investments in infrastructure are necessary, rather than merely sufficient, for a nation to experience a rise in its standard of living. But a nation’s standard of living could improve for other reasons, without investments in infrastructure.
E
nations often experience short-term crises that require that resources be diverted to purposes other than the maintenance and improvement of infrastructure
Like (B) and (C) this may be true, but it doesn’t impact the argument. Even if a nation can’t invest in infrastructure, it doesn’t affect the conclusion that such investments are necessary for a higher standard of living.
Campisi: I find your inference unconvincing; several leavens other than yeast could have been known in 1200 B.C.
Summarize Argument: Counter-Position
Campisi concludes that Yang is not justified in inferring that yeast was known as a leaven in 1200 B.C. just because leavens were known at that time. Why? Because, according to Campisi, other leavens than yeast could have been known in 1200 B.C.
Describe Method of Reasoning
Campisi undermines Yang’s conclusion by introducing an alternative explanation to account for Yang’s evidence. The evidence only shows that some unspecified leaven was used in 1200 B.C., so by pointing out the possibility that other leavens than yeast could have been known at that time, Campisi offers an alternative explanation.
A
suggesting that an alternative set of evidence better supports Yang’s conclusion
Campisi isn’t trying to support Yang’s conclusion, but rather to undermine it. Also, Campisi never proposes alternative evidence.
B
questioning the truth of a presumption underlying Yang’s argument
Yang presumes that there are no alternative leavens other than yeast that could have been known in 1200 B.C. By introducing other leavens as an alternative explanation for Yang’s evidence, Campisi questions that presumption.
C
denying the truth of Yang’s conclusion without considering the reason given for that conclusion
Campisi does consider the evidence behind Yang’s conclusion, and rejects its support for Yang’s conclusion on the grounds that there are alternative explanations available. Also, Campisi never denies the truth of Yang’s conclusion—unsupported doesn’t mean false.
D
pointing out that the premises of Yang’s argument more strongly support a contrary conclusion
Campisi does not argue that another specific conclusion is supported by Yang’s premises, only that Yang’s conclusion is not convincing based on its premises.
E
calling into question the truth of the evidence presented in Yang’s argument
Campisi does not question the evidence that a leaven was known in 1200 B.C., only offers alternative possible explanations for that evidence in order to question Yang’s conclusion.
Summarize Argument
The researcher concludes that watching too much TV increases the risk of developing personality disorders. He supports this by saying that people with certain personality disorders have more theta brain waves, and watching TV increases theta brain waves.
Identify and Describe Flaw
This is the cookie-cutter flaw of assuming that correlation proves causation. The researcher points out a correlation between theta brain waves and personality disorders, then assumes that theta brain waves cause those disorders. He concludes that since TV increases theta brain waves, it must also increase the risk of personality disorders.
In reality, personality disorders might cause the increase in theta waves, or another factor could be causing both. In either of these cases, the researcher’s link between watching TV and developing personality disorders falls apart.
A
uses the phrase “personality disorders” ambiguously
The researcher uses the phrase “personality disorders” clearly and consistently. Its meaning doesn’t shift throughout his argument.
B
fails to define the phrase “theta brain waves”
The researcher doesn't define “theta brain waves,” but he doesn’t need to. (B) doesn’t describe why his reasoning is questionable.
C
takes correlation to imply a causal connection
The author takes the correlation between theta brain waves and certain personality disorders to imply that theta brain waves cause those disorders. It’s possible, however, that the personality disorders cause theta brain waves or that some other factor causes them both.
D
draws a conclusion from an unrepresentative sample of data
We don’t know the sample size of the researcher’s data and we can’t simply assume that his data is unrepresentative.
E
infers that watching TV is a consequence of a personality disorder
Actually, the researcher infers that developing a personality disorder could be a consequence of watching TV. (E) has this backward.
"Surprising" Phenomenon
Why does Lake Laberge, in Canada, contain high levels of toxaphene when toxaphene was banned in North America in the 1980s and is now used only in a few other parts of the world?
Objective
The correct answer must help explain why Lake Laberge contains high levels of toxaphene even though the substance was banned in Canada in the 1980s. The correct answer will either discuss how toxaphene from the past has remained in the lake, is still being produced in or near the lake, or is being introduced to the lake from somewhere else.
A
Levels of pesticides in the environment often continue to be high for decades after their use ends.
If (A) is true, the high levels of toxaphene currently found in Lake Laberge could just be left over from before Canada’s toxaphene ban.
B
Lake Laberge’s water contains high levels of other pesticides besides toxaphene.
We’re not concerned with other pesticides. We just want to know why there are high levels of toxaphene in the lake when toxaphene has been banned in Canada since the early 1980s.
C
Toxic chemicals usually do not travel large distances in the atmosphere.
It doesn’t matter how far toxic chemicals usually travel. The distance toxic chemicals travel doesn’t help explain why Lake Laberge currently contains high levels of toxaphene when the substance has been banned in Canada since the early 1980s.
D
North American manufacturers opposed banning toxaphene.
Whether North American manufacturers supported or opposed the ban is irrelevant. We want to know why Lake Laberge contains high levels of toxaphene all these years after the ban.
E
Toxic chemicals become more readily detectable once they enter organisms the size of fish.
The stimulus never discusses fish. It only discusses how a lake in Canada contains high levels of toxaphene even though toxaphene was banned in Canada in the early 1980s.
Summary
The stimulus can be diagrammed as follow:
Notable Valid Inferences
Samantha’s friends can either like green tea, like oolong tea, or like neither.
A
Samantha likes black tea.
This could be true. We don’t know Samantha’s opinion on black tea.
B
None of Samantha’s friends likes green tea.
This could be true. Oolong and green tea have a “not both” relationship, meaning that Samantha’s friends can like oolong tea, green tea, or neither.
C
Samantha’s friends like exactly the same kinds of tea as each other.
This could be true. It could be the case that all of Samantha’s friends like green tea and black tea, for example.
D
One of Samantha’s friends likes neither oolong nor green tea.
This could be true. Oolong and green tea have a “not both” relationship, meaning that Samantha’s friends can like oolong tea, green tea, or neither.
E
One of Samantha’s friends likes all the kinds of teas that Samantha likes.
This must be false. As shown below, we know that Samantha’s friends can’t like both oolong and green tea, and Samantha likes both of these kinds of tea.
Summary
The stimulus tells us that the country allows a slower and more natural life than the city. This suggests that country life should be more healthy and relaxed than city life. However, surveys show that country and city dwellers experience equal levels of illness and stress.
Strongly Supported Conclusions
These facts allow us to infer that:
A slower and more natural rhythm of life does not necessarily decrease rates of illness and stress.
The common wisdom that country life is healthier and more relaxed than city life is not supported by data.
A slower and more natural rhythm of life does not necessarily decrease rates of illness and stress.
The common wisdom that country life is healthier and more relaxed than city life is not supported by data.
A
Living in the country is neither healthier nor more relaxing than living in the city.
This is strongly supported. The facts given show that there’s no real difference between the country and the city in illness frequency and severity (i.e. health), nor in stress (i.e. relaxation). Thus, country living is not healthier or more relaxing than city living.
B
Living in the country does not in fact permit a slower and more natural rhythm of life than living in the city.
This is not supported. The stimulus doesn’t contradict that living in the country offers a slower and more natural rhythm of life. The issue is just that that rhythm doesn’t appear to improve health or stress levels.
C
People whose rhythm of life is slow and natural recover quickly from illness.
This is not supported. The facts suggest nothing about how fast people recover from illness, either in the country (with a slow and natural rhythm of life) or otherwise. We just can’t say.
D
Despite what people believe, a natural rhythm of life is unhealthy.
This is anti-supported. Based on what we know, a natural rhythm of life just doesn’t make a difference to health. That means it’s neither particularly healthy nor unhealthy.
E
The amount of stress a person experiences depends on that person’s rhythm of life.
This is anti-supported. The stimulus shows us that having a slow and natural rhythm of life makes no difference to people’s stress levels. This indicates that stress does not depend on someone’s rhythm of life.
Summarize Argument: Counter-Position
The industrialist concludes that his factory’s emissions are not a health risk to nearby residents. He supports this by saying that the only testimony about the emissions comes from local residents, but only a trained scientist can assess the danger, and none of the residents are scientists.
Identify and Describe Flaw
The industrialist’s reasoning is flawed because he fails to provide any evidence for his conclusion. Even if the residents’ testimonies cannot prove that the emissions are a health risk, the industrialist still needs to provide evidence for the conclusion that the emissions are not a health risk.
In other words, he assumes that the environmentalists’ conclusion is false simply because their support is weak.
A
impugns the motives of the residents rather than assessing the reasons for their contention
This is the cookie-cutter “ad hominem” flaw, where the author attacks the person or group making the argument, rather than the argument itself. The industrialist doesn’t make this mistake. He attacks his opponents’ support and doesn’t make any assumptions about their motives.
B
does not consider the safety of emissions from other sources in the area
The argument is only about the safety of emissions from the industrialist’s factory. Emissions from any other sources are irrelevant.
C
presents no testimony from scientists that the emissions are safe
The industrialist fails to provide any evidence for his conclusion that the emissions are safe. He claims that only scientists can testify that the emissions are safe, but he never actually presents any scientists’ testimonies.
D
fails to discuss the benefits of the factory to the surrounding community
The industrialist only concludes that the factory’s emissions do not present a health risk. He doesn’t need to discuss any benefits of the factory to the community.
E
equivocates between two different notions of the term “health risk”
The industrialist doesn’t make this mistake. He uses the term “health risk” clearly and consistently throughout his argument.
"Surprising" Phenomenon
Why did trade double in Glasgow between 1750 and 1765?
Objective
The correct answer will be the only answer that doesn’t help explain why trade doubled in Glasgow between 1750 and 1765. The correct answer could give irrelevant information that fails to help explain the doubling or information that makes the doubling seem more confusing.
A
The technological revolution that started in the early eighteenth century in England resulted in increased trade between England and Scotland.
If (A) is true, trade doubling in Glasgow between 1750 and 1765 could have resulted from a general increase in trade between Scotland and England because of the technological revolution.
B
Reductions in tariffs on foreign goods in 1752 led to an increase in imports to Glasgow.
Imports are part of trade, so if (B) is true, the increase in imports to Glasgow because of the reductions in tariffs could help explain why trade doubled in Glasgow between 1750 and 1765.
C
The establishment of banking in Glasgow encouraged the use of paper money, which made financial transactions more efficient.
Financial transactions becoming more efficient could make trade easier to complete and, therefore, help explain why trade doubled in Glasgow between 1750, when its first bank was established, and 1765.
D
Improvements in Scottish roads between 1750 and 1758 facilitated trade between Glasgow and the rest of Scotland.
If (D) is true, the ease of transportation afforded by improvements made to roads in Scotland between 1750 and 1758 could help explain the increase in trade in Glasgow between 1750 and 1765.
E
The initial government regulation of Scottish banks stimulated Glasgow’s economy.
The initial government regulation of Scottish banks didn’t occur until 1765. We’re focused on why trade doubled in Glasgow between 1750 and 1765, so (E) is irrelevant.