Summarize Argument: Phenomenon-Hypothesis
The author hypothesizes that the decrease in mourning-dove population is probably a result of the loss of nesting habitat. This is based on the fact that many doves had formerly nested in the nearby orchards, but the doves stopped building nests in the orchards after sprinklers were installed in the orchards.
Notable Assumptions
The author assumes that the doves’ stopping of nests in the orchards constitutes a loss of nesting habitat. The author also assumes that there aren’t enough other areas for doves to build nests that could make up for the loss of the orchards as a nest-building location. The author also assumes there’s no other explanation for the decrease in population aside from loss of nesting habitat.
A
Mourning doves were recently designated a migratory game species, meaning that they can be legally hunted.
If anything, this weakens the argument by providing a potential alternate explanation for the decrease in dove population (they began to be hunted).
B
The trees in the nearby orchards were the only type of trees in the area attractive to nesting mourning doves.
This strengthens by providing evidence that loss of the orchards as a nest-building location constitutes a loss of nesting habitat. If there had been other trees available that were attractive for nesting, then there wouldn’t necessarily be a loss of nesting habitat.
C
Blue jays that had nested in the orchards also ceased doing so after the sprinklers were installed.
This tells us another species stopped nesting in the orchards. But that doesn’t reveal whether the loss of the orchards was a loss of nesting habitat for mourning doves. We already know the doves stopped nesting in the orchards.
D
Many residents of the area fill their bird feeders with canola or wheat, which are appropriate seeds for attracting mourning doves.
This tells us that doves might feed at bird feeders. But it doesn’t have a clear impact on doves’ nesting options and whether their nesting habitat has decreased.
E
Mourning doves often nest in fruit trees.
Are fruit trees in orchards? Are they no longer available for nesting in the orchard? Are there fruit trees outside of the orchards? Without knowing the answers to these questions, (E) has no clear impact.
Summarize Argument
The author concludes that Activate is effective. This is because the makers of Activate offer a free month’s supply to customers, which they wouldn’t do if Activate was ineffective.
Notable Assumptions
In order for the free sample to be in the company’s interest, the author assumes that the makers of Activate don’t get any benefit from the free sample, besides having potential customers try their product. Any hidden benefit, such as an investment agreement the company signed or a cash benefit the company gets from shipping their product, would weaken the author’s argument.
A
The nutrients in Activite can all be obtained from a sufficiently varied and well-balanced diet.
The author never said Activate is necessary. It’s simply a supplement that helps people who may otherwise, for whatever reason, not get those nutrients in their diet.
B
There are less expensive dietary supplements on the market that are just as effective as Activite.
Activate can still be effective even if it’s not the most cost-efficient.
C
A month is not a sufficient length of time for most dietary supplements to be fully effective.
Even if Activate doesn’t show itself to be “fully” effective in a month, it might still prove to be effective.
D
The makers of Activite charge a handling fee that is considerably more than what it costs them to pack and ship their product.
Activate’s makers ingeniously make money from the free sample. This gives us some other reason why the company would choose to offer the free samples.
E
The mere fact that a dietary supplement contains only natural ingredients does not insure that it has no harmful side effects.
The author has no stance on side effects. All that matters is whether sending free samples proves Activate is effective.
Summary
The stimulus can be diagrammed as follows:
Notable Valid Inferences
If the citizens will not have majority ownership for at least one year, then the government should not sell.
If the government is not selling for the highest price on an open market, then it should not sell.
A
The government will sell StateAir, a state-owned airline. The highest bid received was from a corporation that was owned entirely by citizens of Country F when the bid was received. Shortly after the bid was received, however, noncitizens purchased a minority share in the corporation.
This is consistent with the requirements. The corporation in question offered the highest bid for the state-owned airline, and even after noncitizens purchase the share, citizens will still have majority ownership of the company.
B
The government has agreed to sell National Silver, a state-owned mine, to a corporation. Although citizens of Country F have majority ownership of the corporation, most of the corporation’s operations and sales take place in other countries.
This could be consistent with the requirements. This condition meets the requirement of citizens having majority ownership, but we don’t know whether or not the requirement of selling for the highest price was violated.
C
The government will sell PetroNat, a state-owned oil company. World Oil Company has made one of the highest offers for PetroNat, but World Oil’s ownership structure is so complex that the government cannot determine whether citizens of Country F have majority ownership.
This could be consistent with the requirements. It is possible that “one of the highest” means the highest offer, and since the government “cannot determine” if the citizens have majority ownership, we cannot confirm that one of the requirements was violated.
D
The government will sell National Telephone, a state-owned utility. The highest bid received was from a company in which citizens of Country F have majority ownership but noncitizens own a minority share. However, the second-highest bid, from a consortium of investors all of whom are citizens of Country F, was almost as high as the highest bid.
This is consistent with the requirements. The government got the highest bid from a company in which the citizens have majority ownership.
E
The government will sell StateRail, a state-owned railway. The government must place significant restrictions on who can purchase StateRail to ensure that citizens of Country F will gain majority ownership. However, any such restrictions will reduce the price the government receives for StateRail.
This would violate one of the requirements. In this situation, it is impossible to simultaneously meet both of the necessary conditions of selling. If the requirement about citizen ownership is met, the requirement about selling for the highest price must be violated.
Summarize Argument: Counter-Position
The author concludes that the algae-scraping specialization of certain fish species in Flower Lake and Blue lake evolved more than once. This is based on the fact that if the fish in these lakes are closely related, then the algae-scraping specialization evolved only once. But the fish in these lakes are not closely related.
Identify and Describe Flaw
The author confuses a sufficient condition for a necessary condition. The fish being closely related is sufficient for the algae-scraping specialization to have evolved only once. But this doesn’t mean the fish being closely related is necessary. So even if the fish aren’t closely related, it’s still possible the specialization evolved only once.
A
infers a cause merely from a correlation
The argument’s reasoning is based on an attempted application of a conditional rule. There is not conclusion or assumption of a causal relationship from a correlation.
B
infers that just because the evidence for a particular claim has not yet been confirmed, that claim is false
The author doesn’t argue, “We haven’t confirmed the specialization evolved only once, so it must have evolved more than once.”
C
takes a sufficient condition as a necessary one
The author takes a sufficient condition (fish being closely related) for the specialization being evolved only once as a necessary condition. This is flawed because even if the fish are not closely related, the specialization still could have evolved only once.
D
infers merely because something was likely to occur that it did occur
The author doesn’t argue, “The specialization is likely to have evolved more than once. So it must have evolved more than once.”
E
appeals to the authority of biologists who may not be representative of all biologists with expertise in the relevant area
The author’s reasoning doesn’t rely on the authority of biologists. It relies on the attempted application of a conditional statement.
Letter to the editor: When your newspaper reported the (admittedly extraordinary) claim by Mr. Hanlon that he saw an alien spaceship, the tone of your article was very skeptical despite the fact that Hanlon has over the years proved to be a trusted member of the community. If Hanlon claimed to have observed a rare natural phenomenon like a large meteor, your article would not have been skeptical. So your newspaper exhibits an unjustified bias.
Summary
Mr. Hanlon’s claim that he saw an alien spaceship was extraordinary.
The newspaper reported on this claim with a skeptical tone.
Mr. Hanlon has proved to be a trusted member of the community.
Hanlon claimed to have seen a rare natural phenomenon→ /Article would have skeptical
The newspaper exhibits unjustified bias.
Notable Valid Inferences
If the article was skeptical, then Hanlon’s claim wouldn’t have been about a rare natural phenomenon.
A
If a claim is extraordinary, it should not be presented uncritically unless it is backed by evidence of an extraordinarily high standard.
The letter conflicts with the principle in (A), which gives sufficient conditions for the newspaper to be skeptical. Hanlon’s situation met these conditions, so the newspaper should be skeptical. Yet, the letter argues the opposite—that the newspaper should not be skeptical.
B
One should be skeptical of claims that are based upon testimonial evidence that is acquired only through an intermediary source.
This principle does not apply. (B) discusses testimonial evidence acquired only through an intermediary source, but Hanlon’s evidence was provided directly.
C
If a media outlet has trusted a source in the past and the source has a good reputation, the outlet should continue to trust that source.
This principle does not apply. We know that Hanlon has been a trusted member of the community, but we don’t know if this newspaper has trusted Hanlon as a source in the past. We also don’t know anything about the newspaper’s reputation.
D
People who think they observe supernatural phenomena should not publicize that fact unless they can present corroborating evidence.
This principle does not apply to the letter’s argument. The argument in the letter is about the newspaper’s bias, but the principle in (D) would pertain to Hanlon’s actions.
E
A newspaper should not publish a report unless it is confirmed by an independent source.
This principle does not apply. (E) gives a principle for determining when a report shouldn’t be published, but the letter isn’t arguing about whether or not the report should have been published. Instead, the letter’s argument is about the newspaper’s bias.
Summarize Argument
The author concludes that global recessions can never be prevented. This is based on the following:
In order to prevent global recessions, it must be the case that those recessions are predictable.
Economist using the best techniques available consistently fail to predict global recessions.
Identify and Describe Flaw
The author assumes that the fact economists have not yet been able to predict global recessions implies that such recession are unpredictable. This overlooks the possibility that the recessions might be predictable, just not with the “best techniques at [the economists’] disposal.” Perhaps better techniques will be developed in the future that will predict recessions. More generally, the assumption is that past failures to predict show that prediction is impossible.
A
presupposes in a premise the conclusion that it purports to establish
(A) describes circular reasoning. But the author’s conclusion is not assumed to be true in the premises. The conclusion is that recessions can never be prevented; this claim isn’t repeated in the premises.
B
fails to establish that economists claim to be able to accurately predict global recessions
The author didn’t need to establish this, because no part of the argument assumed that any economists claimed the ability to predict recessions.
C
treats the predictability of an event, which is required for the event to be preventable, as a characteristic that assures its prevention
The author didn’t argue that, because the necessary condition for preventability is met (predictability), that the thing (predictability) is sufficient for preventing recessions. Rather, the author assumes that the necessary condition for preventing recessions has not been met.
D
fails to address the possibility that the techniques available to economists for the prediction of global recessions will significantly improve
This possibility, if true, would show why economists might be able to predict recessions accurately in the future, even if they haven’t been able to so far using the best available techniques. (D) points out that past failures to predict do not imply that prediction is impossible.
E
implicitly bases an inference that something will not occur solely on the information that its occurrence is not predictable
The author doesn’t present any “information” that recessions are “not predictable.” He assumes they aren’t predictable, but this isn’t what the premises actually establish. Also, the conclusion is not that recessions won’t occur; it’s that they can’t be prevented.
Summarize Argument
The author concludes that the pineal gland produces less melatonin as it ages. This is based on a study of people aged 65-81 suffering from insomnia. The study showed that most insomnia symptoms in these people are reduced by eating melatonin. Melatonin is a hormone produced by the pineal gland, and it has a role in regulating the body’s biological block.
Identify and Describe Flaw
The author assumes that the melatonin of people in the study is lower than those levels would have been when those people were younger. The author also assumes that people in the study, who all have insomnia, are representative of people generally with respect to melatonin at the corresponding age (65-81). This overlooks the possibility that the study’s subjects have unusually low melatonin (which might be why they have insomnia). An average person might not have low insomnia at 65-81.
A
infers from the effect of an action that the action is intended to produce that effect
The author does not make any assumptions about intentions. Whether people take melatonin because they intended to reduce insomnia symptoms doesn’t matter. We know that eating melatonin did reduce symptoms in the study.
B
relies on the opinions of individuals who are likely to be biased
The argument doesn’t rely on opinions to support the conclusion. The conclusion happens to refer to the claims of manufacturers, but this reference is not used as part of the reason to believe that the pineal gland produces less melatonin as it ages.
C
depends on using two different meanings for the same term to draw its conclusion
There is no term that is used in two different ways. “Insomnia,” “melatonin,” “pineal gland” all have consistent meanings.
D
confuses an effect of a phenomenon with its cause
It’s not clear what (D) refers to. In any case, we don’t know know from the premises that any causal relationship is reversed. Does lower melatonin cause insomnia, or is it reversed? We don’t know, so can’t say that the author is confusing an effect for a cause.
E
relies on a sample that is unrepresentative
The study only included people with insomnia, and only included people 65-81. We don’t know whether people with insomnia have unusually low melatonin for their age. And we don’t know whether the melatonin levels change by age, since the study didn’t evaluate younger people.
Summarize Argument: Counter-Position
The author implicitly concludes that proponents of jury nullification are wrong. He supports this by claiming that jury nullification depends too much on jurors’ objectivity and that juries too often make serious mistakes when deciding to acquit based on perceived unfairness.
Describe Method of Reasoning
The author undermines the proponents of jury nullification by pointing out that the doctrine has negative consequences— overreliance on jurors’ objectivity and a tendency for juries to make serious mistakes based on perceived unfairness.
A
attacking the motives of the proponents of the doctrine
The author never attacks the motives of the proponents of jury nullification. He just undermines their position by pointing out negative consequences of the doctrine.
B
identifying an inconsistency within the reasoning used to support the position
The author doesn’t point out any inconsistencies in the proponents’ reasoning. He just points out the consequences of their position.
C
attempting to show that a premise put forward in support of the position is false
The proponents’ premise is that jury nullification is legitimate “because it helps shield against injustice.” The author never argues that this is false, and we can’t presume that his argument implies that it’s false. Instead, he highlights negative consequences of the doctrine.
D
presenting a purported counterexample to a general claim made by the doctrine’s proponents
The author never presents a counterexample to the proponents’ claim. He just presents consequences of jury nullification.
E
arguing that the application of the doctrine has undesirable consequences
The author undermines the proponents’ conclusion by arguing that the application of the doctrine has undesirable consequences— overreliance on jurors’ objectivity and a tendency for juries to make serious mistakes based on perceived unfairness.