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.
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
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
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.