Summarize Argument
We are asked to supply an additional premise to fill in the blank.
The author concludes that gardeners can boost potato yields by planting stinging nettles nearby. He explains that nettles attract insects that kill harmful pests. Although nettles also attract aphids, many of which can harm potatoes, the author says this doesn't contradict his recommendation because _______.
Notable Assumptions
The author assumes that the nettles don’t harm the potato plants. He also assumes that, just because the nettles attract insects that kill pests, this will directly boost potato yields.
To effectively fill in the blank, the correct answer must somehow show that the aphids that are attracted to stinging nettles either don’t harm potato plants or else don’t harm them enough to affect their potato production.
To effectively fill in the blank, the correct answer must somehow show that the aphids that are attracted to stinging nettles either don’t harm potato plants or else don’t harm them enough to affect their potato production.
A
stinging nettles require little care and thus are easy to cultivate
Irrelevant— this fails to show that the aphids that are attracted to nettles do not harm potato yields. Also, whether nettles are easy or difficult to cultivate doesn’t impact the argument that planting them can increase potato yields.
B
some types of aphids are attracted to stinging nettle plants but do not damage them
Irrelevant— this addresses whether some of the aphids damage the nettles, but it fails to address whether the aphids damage the potato plants.
C
the types of aphids that stinging nettles attract do not damage potato plants
If the aphids that are attracted to the nettles do not damage potato plants, then the aphids don’t contradict the author’s recommendation to plant nettles nearby in order to boost potato yields.
D
insect pests typically cause less damage to potato plants than other harmful organisms do
Even if insect pests cause less damage than other organisms, they might still cause a lot of damage. (D) fails to address whether the aphids that are attracted to the nettles damage potato plants enough to reduce their potato yield.
E
most aphid species that are harmful to potato plants cause greater harm to other edible food plants
Irrelevant— it doesn't matter how much harm aphids cause to other plants. The argument is only about increasing the yield of potato plants, and (E) fails to show whether the aphids harm potato plants enough to reduce their yield.
Summarize Argument: Phenomenon-Hypothesis
The zookeeper hypothesizes that Jocko’s silence was meant to keep the other chimpanzees from taking his food. She supports this by showing that Jocko only remained silent after an earlier incident, where his bunch of bananas were taken away by other chimpanzees after he barked excitedly.
Notable Assumptions
The zookeeper assumes that the difference between Jocko’s reactions weren’t a result of getting a different quantity of food: the first day he gets a bunch of bananas, whereas the second he gets only one. This means the zookeeper doesn’t believe that Jocko was actively trying to share his food the first time, or that the quantity of food itself didn’t cause him to bark out of excitement.
A
Chimpanzees utter food barks only when their favorite foods are available.
Jocko received bananas both times. He didn’t bark the second time.
B
Chimpanzees utter food barks only when they encounter a sizable quantity of food.
Jocko wasn’t trying to keep the others from taking his food the second time. He simply hadn’t received a sufficient quantity of food to utter a food bark.
C
Chimpanzees frequently take food from other chimpanzees merely to assert dominance.
Perhaps that’s what happened the first time, but we don’t care. We’re looking for something to weaken the claim that Jocko didn’t bark the second time to keep other chimpanzees from taking his food.
D
Even when they are alone, chimpanzees often make noises that appear to be signals to other chimpanzees.
Jocko didn’t make any noise the second time. We need to know why.
E
Bananas are a food for which all of the chimpanzees at the zoo show a decided preference.
We need to weaken the zookeeper’s claim that Jocko kept quiet to protect his food. This just tells us all chimps like bananas.
Summarize Argument
The argument concludes that trends in publishing are not based on the true interests of the public. This is based on the claim that journalism students are more interested in different stories than the ones that are most commonly published.
Identify and Describe Flaw
This is a cookie-cutter unrepresentative sampling flaw. Journalism students’ tastes in stories are not likely to represent the general public’s interests: they will probably be more interested in serious political and governmental issues, even if the public is truly interested in trends and gossip. So, this survey does not really support the conclusion that publishing is based on false assumptions about public interests.
A
It takes what is more likely to be the effect of a phenomenon to be its cause.
The argument never discusses or relies on the idea of cause and effect relationships.
B
It regards the production of an effect as incontrovertible evidence of an intention to produce that effect.
The argument doesn’t involve any questions of whether an effect was caused intentionally or not.
C
It relies on the opinions of a group unlikely to be representative of the group at issue in the conclusion.
The argument uses the opinions of journalism students to draw a conclusion about the general public’s journalism preferences. This is likely to be an unrepresentative sample.
D
It employs language that unfairly represents those who are likely to reject the argument’s conclusion.
The argument never refers in any way, fairly or unfairly, to those who are likely to reject the argument’s conclusion.
E
It treats a hypothesis as fact even though it is admittedly unsupported.
The argument doesn’t treat an unsupported hypothesis as a fact. In fact, there isn’t any stated hypothesis which the argument admits is unsupported to begin with.
"Surprising" Phenomenon
Why do experts recommend other pest-control methods when bug zappers are very effective?
Objective
A hypothesis resolving this discrepancy will give a reason for pest control experts to prefer birds and insecticides over bug zappers. It will give a reason to avoid bug zappers despite their general effectiveness, or imply that insect-eating birds and insecticides are even more effective.
A
Insect-eating birds will take up residence in any insect-rich area if they are provided with nesting boxes, food, and water.
This does not explain why experts recommend insect-eating birds over bug zappers. It explains why the birds are effective pest-control measures, but makes no comparison with bug zappers.
B
Bug zappers are less effective against mosquitoes, which are among the more harmful insects, than they are against other harmful insects.
This does not provide a reason to favor insect-eating birds and insecticides because it takes no position on the effectiveness of those measures against mosquitos. It is possible birds and insecticides are equally or even less effective against mosquitos.
C
Bug zappers use more electricity but provide less light than do most standard outdoor light sources.
This does not explain why experts would avoid recommending bug zappers as a form of pest control. There is no evidence that pest control experts make their recommendations based on the solutions’ efficiency at turning electricity into light.
D
Bug zappers kill many more beneficial insects and fewer harmful insects than do insect-eating birds and insecticide sprays.
This explains why experts recommend birds and insecticides over bug zappers. Though effective in general, bug zappers are less effective than birds and insecticides at targeting and eliminating insects that are pests.
E
Developers of certain new insecticide sprays claim that their products contain no chemicals that are harmful to humans, birds, or pets.
This does not explain why insecticides or birds are favored by pest-control experts over bug zappers. It does not state that insecticides are any safer than bug zappers.
Summary
The stimulus can be diagrammed as follows:
Notable Valid Inferences
Vacuum tubes are not currently preferable to semiconductors for use in digital circuits.
A
Vacuum tubes are not now preferable to semiconductors for use in digital circuits.
Must be true. In order to be preferable to semiconductors for use in digital circuits, vacuum tubes would to be comparable to semiconductors in all significant respects. Because vacuum tubes are not comparable in terms of current capacity, they are not now preferable.
B
Once vacuum tubes and semiconductors have comparable maximum current capacity, vacuum tubes will be used in some digital circuits.
Could be false. We don’t know if vacuum tubes are comparable to semiconductors in all other significant respects, so we don’t know if they would be preferable even with increased current capacity. Even if they were preferable, that doesn’t necessarily mean they would be used.
C
The only reason that vacuum tubes are not now used in digital circuits is that vacuum tubes’ maximum current capacity is too low.
Could be false. The stimulus doesn’t tell us whether or not vacuum tubes are comparable to semiconductors in any way other than current capacity and heat resistance—maybe they’re deficient in other respects!
D
Semiconductors will always be preferable to vacuum tubes for use in many applications other than digital circuits.
Could be false. The stimulus tells us absolutely nothing about whether or not semiconductors are preferable to vacuum tubes in applications other than digital circuits.
E
Resistance to heat is the only advantage that vacuum tubes have over semiconductors.
Could be false. Maybe vacuum tubes have other advantages besides heat resistance! The stimulus does not rule out this possibility.
Summarize Argument: Phenomenon-Hypothesis
The author hypothesizes that the cause of the Athenian epidemic can be identified, and implies that the cause was the Ebola virus. This is because accounts of the epidemic note hallmarks of the Ebola virus, including a symptom—hiccups—unique to the Ebola virus.
Notable Assumptions
For the cause of the Athenian epidemic to be identified as the author claims, what’s currently known of the Ebola virus must not contradict accounts of the Athenian epidemic. This means that notable symptoms of the Ebola virus must appear in those accounts, while the accounts cannot include symptoms that are not known to derive from the Ebola virus. The author must believe that these accounts are accurate. He must also believe that the Athenian epidemic couldn’t have been caused by a presently unknown disease.
A
Victims of the Ebola virus experience many symptoms that do not appear in any of the accounts of the Athenian epidemic.
The disease that appears in accounts of the Athenian epic is different than what’s known of diseases caused by the Ebola virus. This suggests a different, perhaps unknown virus caused the epidemic.
B
Not all of those who are victims of the Ebola virus are afflicted with hiccups.
The author never says every Ebola victim gets the hiccups—hiccups are just a common symptom. This exception doesn’t undermine the author’s argument.
C
The Ebola virus’s host animals did not live in Athens at the time of the Athenian epidemic.
The Ebola host wasn’t in Athens during the epidemic. Thus, it’s unlikely Ebola caused the epidemic.
D
The Ebola virus is much more contagious than the disease that caused the Athenian epidemic was reported to have been.
This says the disease that caused the Athenian epidemic differs substantially from what we know about Ebola. Thus, that disease likely wasn’t caused by the Ebola virus.
E
The epidemics known to have been caused by the Ebola virus are usually shorter-lived than was the Athenian epidemic.
This says that the Athenian epidemic differs from what we know about Ebola. Thus, Ebola likely didn’t cause the Athenian epidemic.
Summarize Argument: Counter-Position
The letter to the editor supports environmentalists after an article criticized their claims, calling that article’s criticism unjustified. The author claims the environmentalists were correct in claiming that that more wolves on Vancouver Island are killed by hunters than are born annually, even though the population has stayed constant. The reason the criticism is unjustified is because it does not recognize that environmentalists have been introducing new wolves over the past 20 years. (This would make population constancy an inaccurate representation of birth rates.)
Identify Conclusion
The conclusion is the author’s evaluation of the article’s claims: “Your article was unjustified in criticizing environmentalists for claiming that more wolves on Vancouver Island are killed by hunters than are born each year.”
A
Environmentalists have been successfully maintaining the wolf population on Vancouver Island for 20 years.
This is evidence that shows why the wolf population remains constant. The author presents this explanation to show that the environmentalists’ claims about birth and hunting rates could still be accurate.
B
As many wolves on Vancouver Island are killed by hunters as are born each year.
This is the claim discussed in the context. The editor criticizes it, and the author concludes that the criticism of the claim is unjustified.
C
The population of wolves on Vancouver Island should be maintained by either reducing the number killed by hunters each year or introducing new wolves into the population.
The stimulus does not conclude how the wolf population should be maintained. It uses how it is currently being maintained as evidence for the conclusion, which centers on the justification of criticism.
D
The recent studies indicating that the total number of wolves on Vancouver Island has remained roughly constant for 20 years were flawed.
This is inaccurate. The author does not claim that the studies that show the population remaining constant are flawed. The author accepts and presents an explanation for these results.
E
The stability in the size of the Vancouver Island wolf population does not warrant the article’s criticism of the environmentalists’ claim.
This accurately paraphrases the conclusion. The article’s criticism of the environmentalists’ claim - which relies on the stability of the wolf population as evidence - is not justified.
Computer scientist: For several decades, the number of transistors on new computer microchips, and hence the microchips’ computing speed, has doubled about every 18 months. However, from the mid-1990s into the next decade, each such doubling in a microchip’s computing speed was accompanied by a doubling in the cost of producing that microchip.
Summary
For several decades, the number of transistors on computer microchips has doubled every 18 months.
For several decades, microchips’ computing speed has also doubled every 18 months.
From the mid-1990s into the next decade, the cost of producing a microchip doubled each time the microchip’s computing speed doubled.
Very Strongly Supported Conclusions
From the mid-1990s into the next decade, the cost of producing a microchip doubled every 18 months.
From the mid-1990s into the next decade, the cost of producing a microchip doubled each time the number of transistors on a microchip doubled.
A
The only effective way to double the computing speed of computer microchips is to increase the number of transistors per microchip.
Unsupported. Doubling the number of transistors on a microchip is one effective way to double the computing speed of that microchip, but it’s not necessarily the only effective way.
B
From the mid-1990s into the next decade, there was little if any increase in the retail cost of computers as a result of the increased number of transistors on microchips.
Unsupported. We don’t know anything about how the retail cost of computers was affected by the increased number of transistors. We only know that, during this time period, the production cost of microchips doubled each time the number of transistors doubled.
C
For the last several decades, computer engineers have focused on increasing the computing speed of computer microchips without making any attempt to control the cost of producing them.
Unsupported. Just because microchip production costs increased from the mid-1990s into the next decade doesn’t mean that engineers made no effort to control those costs.
D
From the mid-1990s into the next decade, a doubling in the cost of fabricating new computer microchips accompanied each doubling in the number of transistors on those microchips.
Very strongly supported. During this time, production costs doubled each time a microchip’s speed doubled, and speed doubled each time the number of transistors doubled, so we know that production costs doubled each time the number of transistors doubled.
E
It is unlikely that engineers will ever be able to increase the computing speed of microchips without also increasing the cost of producing them.
Unsupported. Just because production costs doubled with microchip speed in the 90s doesn’t mean engineers can’t increase computing speed without raising costs in the future.