Summarize Argument: Phenomenon-Hypothesis
Jim concludes that a substance contains iron because it’s attracted to a magnet, and iron is a material that’s attracted to magnets.
Identify and Describe Flaw
This is a cookie-cutter example of an argument mistaking a sufficient condition for a necessary condition. Jim treats “containing iron” as though it were a necessary condition for being magnetic, even though it’s only sufficient. In other words, he ignores the possibility that the substance contains a magnetic material other than iron.
A
iron sometimes fails to be attracted to magnets
This possibility is irrelevant because the iron was attracted to the magnet in this case.
B
iron is attracted to other objects besides magnets
The argument is only concerned with whether being attracted to a magnet is enough to prove that a substance contains iron. Whether iron is also attracted to other objects has no bearing on that issue.
C
the magnet needed to be oriented in a certain way
Even if this were a requirement, the magnet would have to have been oriented correctly since it attracted the substance in this case.
D
magnets attract substances other than iron
This possibility undermines the conclusion because it means that the substance could be attracted to the magnet because it contains some magnetic material other than iron.
E
some magnets attract iron more strongly than others
The argument is only concerned with whether the magnet attracts the substance or not; the degree to which it attracts it is irrelevant.
Summarize Argument: Phenomenon-Hypothesis
The author hypothesizes that the book Horatio wants must have been either misplaced or stolen. He supports this by saying that the book is missing from its place on the shelf and no one in the library is using it. It also isn’t checked out to a borrower, awaiting shelving, or part of a special display.
Describe Method of Reasoning
The author supports his hypothesis that the book in question was either misplaced or stolen by eliminating alternative explanations for its absence from the shelf.
A
An observation about one object is used as a basis for a general conclusion regarding the status of similar objects.
The author does use an observation about the book Horatio wants, but he uses it to draw a specific conclusion about that same book, not a general conclusion about similar books.
B
A deficiency in a system is isolated by arguing that the system failed to control one of the objects that it was intended to control.
The author doesn't claim that the library system is deficient or that it failed to control the book. He simply argues that, since the book is missing and other explanations for its absence have been ruled out, it must have been misplaced or stolen.
C
A conclusion about a particular object is rebutted by observing that a generalization that applies to most such objects does not apply to the object in question.
The author never rebuts any conclusion about the book; he draws a conclusion by eliminating alternative explanations. He also doesn’t apply any generalizations about most books to the particular book that Horatio wants.
D
A generalization is rejected by showing that it fails to hold in one particular instance.
The author never rejects a generalization, nor does he show that a generalization fails to hold in the particular instance of the missing book. Instead, he supports a particular conclusion about the book.
E
The conclusion is supported by ruling out other possible explanations of an observed fact.
The author supports his conclusion by ruling out other possible explanations of the book's absence. Since no one is using it, it isn't checked out, waiting to be shelved, or part of a display, he concludes that it must have been misplaced or stolen.
Summary
Ten years ago, stricter regulations on power plant emissions were imposed.
If those regulations had been followed, the level of sulfur dioxide in the atmosphere would have decreased.
The level of sulfur dioxide in the atmosphere has increased over the last ten years.
If those regulations had been followed, the level of sulfur dioxide in the atmosphere would have decreased.
The level of sulfur dioxide in the atmosphere has increased over the last ten years.
Very Strongly Supported Conclusions
The emissions regulations have not been followed.
A
If current regulations on emissions from coal-burning power plants are not followed from now on, then the level of sulfur dioxide in the atmosphere will continue to increase.
Unsupported. The level of sulfur dioxide increased because the regulations were not followed, but we don’t know what might happen if the regulations are not followed from now. Sulfur dioxide might continue to increase, or it might level out, or something else might reduce it.
B
There have been violations of the regulations on emissions from coal-burning power plants that were imposed ten years ago.
Very strongly supported. If the regulations had been followed, the level of sulfur dioxide in the atmosphere would have decreased. But the level of sulfur dioxide has increased, so the regulations must not have been fully followed.
C
If the regulations on emissions from coal-burning power plants are made even stronger, the level of sulfur dioxide in the atmosphere still will not decrease.
Unsupported. The stimulus doesn’t tell us anything about what might happen if regulations are made stronger. We only know that if the original regulations had been followed, then sulfur dioxide levels would have decreased.
D
Emissions from coal-burning power plants are one of the main sources of air pollution.
Unsupported. Power point emissions caused an increase in the level of sulfur dioxide in the atmosphere, but we don’t know that they’re one of the main sources of air pollution.
E
Government regulations will never reduce the level of sulfur dioxide in the atmosphere.
Unsupported. The regulations imposed ten years ago didn’t successfully reduce the level of sulfur dioxide in the atmosphere, but that doesn’t mean that government regulations will never reduce it.
Summarize Argument: Counter-Position
Other people think that as active landfills are closed over the next ten years, there will be a serious shortage of usable landfills. The author concludes that this belief is unsound. The author supports this conclusion by asserting that the belief is based on the assumption that no new landfills will open over the next ten years, and by asserting that this assumption is unlikely to be true.
Identify Argument Part
The referenced text is other people’s position. They think that there will be a shortage of landfills because many active landfills will be closed over the next ten years.
A
It follows from the claim stated in the argument’s first sentence.
The referenced text does not follow from the first sentence. It doesn’t follow from any claim in the stimulus. Some people think it follows from the claim that landfills will close over the next decade, but the author’s point is that it does not follow from that claim.
B
It is the main conclusion of the argument.
The author’s conclusion criticizes the referenced text.
C
It establishes the truth of the argument’s conclusion.
The referenced text does not support the author’s conclusion. It’s criticized by the author’s conclusion.
D
It is a claim on which the argument as a whole is designed to cast doubt.
This accurately describes the role of the referenced text. The author’s argument criticizes the view that there will be an inevitable crisis of landfill availability.
E
It is an intermediate conclusion of the argument.
The referenced text is not a premise or a conclusion of the author’s argument. It’s criticized by the author’s argument.
"Surprising" Phenomenon
Why are residents of X who are reported to have disease P more likely to die from it than are residents of any other country, even though X has the lowest rate of disease P out of all countries?
Objective
The correct answer should help explain why the fatality rate for those reported to have disease P is higher in country X despite the lower rate of disease P in that country.
A
There are several forms of disease P, some of which are more contagious than others.
But are residents of country X more likely to contract the more contagious forms of disease P? In any case, degree of contagiousness doesn’t indicate the deadliness of a disease. It indicates instead the likelihood of spreading to others.
B
Most of the fatal cases of disease P found in Country X involve people who do not reside in Country X.
The statistic in the stimulus concerns residents of country X. So, deaths from people who don’t reside in country X are irrelevant, because they aren’t counted in the statistic.
C
In Country X, diagnosis of disease P seldom occurs except in the most severe cases of the disease.
This could explain both the lower rate of disease P in country X (mild cases go unreported) as well as the higher likelihood of death for those reported to have disease P. The reported cases would be more severe, on average, than cases in other countries.
D
The number of cases of disease P that occur in any country fluctuates widely from year to year.
Varying levels of disease P from year to year doesn’t help explain a lower rate of the disease in country X or why the reported cases are more deadly. We would already expect the number of cases not to be exactly the same every year.
E
Because of its climate, more potentially fatal illnesses occur in Country X than in many other countries.
We’re trying to explain the higher fatality rate of disease P in country X. Other illnesses don’t affect the fatality rate of disease P.
After an oil spill, rehabilitation centers were set up to save sea otters by removing oil from them. The effort was not worthwhile, however, since 357 affected live otters and 900 that had died were counted, but only 222 affected otters, or 18 percent of those counted, were successfully rehabilitated and survived. Further, the percentage of all those affected that were successfully rehabilitated was much lower still, because only a fifth of the otters that died immediately were ever found.
Summarize Argument
The author concludes that the effort to save sea otters by removing oil from them wasn’t worthwhile. He supports this by saying that only 18% of counted otters were successfully rehabilitated and that this percentage is actually even lower because only a fifth of the otters that died immediately were ever found.
Notable Assumptions
The author assumes that a low success rate means that the rehabilitation effort wasn’t worthwhile, ignoring the possibility that a small number of rehabilitated otters might have significant positive ecological value or long-term benefits.
He also assumes that the reported number of otters is accurate, without addressing the possibility that the dead otters that were never found can’t be accurately counted. (?)
Note: We’re looking for the answer choice that “calls into question evidence offered in support of the conclusion.”
A
Do sea otters of species other than those represented among the otters counted exist in areas that were not affected by the oil spill?
The author’s argument only addresses rehabilitation efforts among the otter population that was affected by the oil spill. Surely other otter species exist in other places, but their existence doesn’t call into question the evidence offered in support of the author’s conclusion.
B
How is it possible to estimate, of the sea otters that died, how many were not found?
This calls into question the author’s evidence. He claims that the percentage of successfully rehabilitated otters is much lower than 18% because only a fifth of the dead otters were ever found. But how can he know that this number is accurate if the otters were never found?
C
Did the process of capturing sea otters unavoidably involve trapping and releasing some otters that were not affected by the spill?
Like (A), the author’s argument is only concerned with those otters that were affected by the spill. The effects of the rehabilitation process on other otters doesn’t call into question his evidence, which only addresses affected otters.
D
Were other species of wildlife besides sea otters negatively affected by the oil spill?
The author’s evidence only addresses sea otters that were affected by the oil spill. Whether other species of wildlife were also affected is irrelevant, since the rehabilitation efforts in question only involved sea otters.
E
What was the eventual cost, per otter rehabilitated, of the rehabilitation operation?
The author doesn’t mention cost as a factor in his assessment of whether the rehabilitation effort was worthwhile. (E) thus doesn’t call into question the author’s evidence, which only addresses the percentage of otters that were rehabilitated.