"Surprising" Phenomenon
Parasites in a stingray are not good for the stingray’s health, but the absence of parasites in a stingray is an indicator that the ecosystem the stingray lives in is under environmental stress.
Objective
The right answer will be a hypothesis that reconciles the seemingly contradictory ideas in the stimulus. It will explain how the presence of parasites in a stingray can be an indication of the stingray’s sub-optimal health while the absence of parasites in a stingray can indicate an ecosystem is of sub-optimal health.
A
During part of their life cycles, the parasites of stingrays require as hosts shrimp or oysters, which are environmentally vulnerable organisms.
This helps reconcile the discrepancy. The absence of parasites in a stingray may indicate that, at the necessary point in their life cycles, the parasites could not find a shrimp or oyster to host them, as these potential hosts were adversely affected by environmental stress.
B
A stingray is a free-ranging predator that feeds on smaller organisms but has few predators itself.
This does not offer information about parasites, which are a key feature of the discrepancy.
C
A parasite drains part of the vitality of its host by drawing nourishment from the host.
The stimulus already says that stingrays with parasites are less healthy than they would be without parasites. The discrepancy involves the absence of parasites in stingrays indicating an environmentally stressed ecosystem, which (C) does not discuss.
D
An ecosystem can be considered stressed if only a few species of very simple organisms can live there.
(D) discusses what could cause an ecosystem to be considered stressed. However, it does not provide new information that reconciles the discrepancy. The stimulus also specifically addresses ecosystems under environmental stress, rather than simply being considered stressed.
E
Since the life of parasites depends on that of their host, they need to live without killing their host or else to reproduce and infect other individuals before their own host dies.
This provides insight into the life of parasites, but not into the discrepancy discussed in the stimulus. (E) does not offer information that explains how parasites can be unhealthy for jellyfish but, when absent in jellyfish, indicate an environmentally stressed ecosystem.
Summarize Argument
The argument concludes that not every type of ski injury has seen decreasing numbers, although the number of ski injuries has decreased overall. This is supported with the statistic that knee injuries, which used to represent 11 percent of ski injuries, now represent 16 percent.
Identify and Describe Flaw
This is a cookie-cutter flaw of confusing amounts and percentages. The argument’s conclusion is about the amount of different types of ski injuries, but the evidence is only about percentages. However, it’s entirely possible that there are fewer knee injuries now, even though they account for a greater percentage of all ski injuries—for example, because the number of other injury types has just decreased more.
A
It fails to allow for there being ski injuries other than broken legs, ankle injuries, and knee injuries.
The argument only uses these three types of injuries as examples, it never claims that they’re the only types of ski injuries.
B
It infers disparate effects from the same single cause.
The argument is only concerned with one cause and one effect: the cause is improvements in ski equipment, and the effect is a lower number of ski injuries.
C
It ignores the possibility that the number of skiers has increased over the past 20 years.
The argument states that ski injuries have decreased by 50 percent over the past 20 years, regardless of the number of skiers. Also, the percentage statistics the argument cites are unaffected by the number of skiers.
D
It assumes that an increase in the proportion of knee injuries rules out a decrease in the number of knee injuries.
The argument concludes that certain types of injuries have not decreased in number, and uses knee injuries as an example based on an increased percentage. This ignores the possibility that there are still fewer knee injuries, even though the percentage is higher.
E
It proceeds as though there could be a greater decrease in injuries in each category of injury than there is in injuries overall.
The argument never acts as though every category of injury could see a greater decrease than the overall decrease.
Summarize Argument
The author concludes that the switch to synthetic piano keys won’t do much to stop the killing of elephants for their ivory. This is because piano makers have never been major consumers of ivory.
Notable Assumptions
The author assumes that only major consumers can help stop the killing of elephants for their ivory. This means that the synthetic ivory won’t be able to replace real ivory used in other industries.
A
Most people who play the piano but are not concert pianists can nonetheless easily distinguish between the new synthetic ivory and inferior ivory substitutes.
We don’t care what average piano players can do. We already know the new synthetic ivory is superior.
B
The new synthetic ivory can be manufactured to resemble in color and surface texture any of the various types of natural ivory that have commercial uses.
This suggests the synthetic ivory could make a difference in the global ivory trade. We’re trying to strengthen the opposite claim.
C
Other natural products such as bone or tortoise shell have not proven to be acceptable substitutes for natural ivory in piano keys.
We don’t care what else could be a substitute for ivory. We care about how the new synthetic ivory will factor into the global ivory trade.
D
The most common use for natural ivory is in ornamental carvings, which are prized not only for the quality of their workmanship but also for the authenticity of their materials.
The most common use for natural ivory is in an industry that cares about authentic ivory. Thus, synthetic ivory won’t make a difference in that industry, which suggests synthetic ivory won’t have a major impact on the global ivory trade.
E
It costs significantly less to produce the new synthetic ivory than it does to produce any of the ivory substitutes that scientists had developed previously.
We don’t care about the cost. We also don’t know how much the new synthetic ivory costs versus real ivory.
Summarize Argument: Counter-Position
The author looks to the disappearance of Norse settlements and concludes, contrary to what some people claim, that the Norse settlements did not disappear as a result of decreasing temperatures. As evidence, the author points out that Inuit settlers inhabiting Greenland during the same time continued to thrive long after the Norse settlers disappeared.
Describe Method of Reasoning
The author counters a position held by others. She does this by providing evidence that is inconsistent with what others claim. Decreasing temperatures could not have been what caused Norse settlements to disappear because Inuit settlements during the same time period were not wiped out.
A
denying the relevance of an analogy
The author does not describe any analogy. The author’s mention of Inuit settlements is a counterexample meant to attack the claim that the Norse settlements were wiped out by decreasing temperatures.
B
producing evidence that is inconsistent with the claim being opposed
The evidence the author produces is that of the Inuit settlements in existence at the same time as the Norse settlements. The claim being opposed is that Greenland became too cold for human habitation.
C
presenting an alternative explanation that purports to account for more of the known facts
The author does not present an alternative explanation. She does not attempt to explain why the Norse settlements in Greenland disappeared.
D
citing a general rule that undermines the claim being opposed
The author does not provide a general rule in order to counter other’s claims. Rather, the author provides the specific instance of Inuit settlements to oppose these claims.
E
redefining a term in a way that is favorable to the argument’s conclusion
The author does not redefine a term, or define any term used.
Summary
The argument concludes that passengers are safer on airplanes with a collision-evasion system equipped, even though the system frequently warns pilots of phantom airplanes. This is supported by the premise that the system warns pilots to evade possible collisions.
Notable Assumptions
The argument assumes that the phantom warnings don’t create more danger than the system prevents. For example, that pilots don’t take dangerous evasion maneuvers in response to phantom warnings.
It also assumes that pilots actually respond to the system’s warnings frequently enough to avoid possible collisions. Otherwise, the system’s presence wouldn’t make much difference to safety at all.
It also assumes that pilots actually respond to the system’s warnings frequently enough to avoid possible collisions. Otherwise, the system’s presence wouldn’t make much difference to safety at all.
A
Passengers feel no safer on airplanes equipped with the radar system than on comparable airplanes not so equipped.
Whether or not passengers feel safer isn’t important to determining whether or not they are safer—in fact, it’s not relevant at all.
B
Warnings given by a collision-avoidance system about phantom airplanes are not caused by distorted radar signals.
The possible cause of phantom airplane warnings doesn’t make any difference to the argument, so can’t be necessary.
C
The frequency of invalid warnings will not cause pilots routinely to disregard the system’s warnings.
For the argument to make sense, pilots have to actually act on the system’s warnings—otherwise the system would make no difference. If we negated this, meaning pilots just ignored the warnings, that would leave the conclusion unsupported.
D
Commercial passenger airplanes are not the only planes that can be equipped with a collision-avoidance system.
Whether or not the system can be equipped on other types of planes is irrelevant to whether it makes commercial air passengers safer.
E
The greatest safety risk for passengers traveling on commercial passenger airplanes is that of a midair collision.
The argument just claims that passengers are safer with the system than without it. Whether that means they’re a lot safer or a little safer doesn’t really matter, so this isn’t a necessary assumption.
Summary
The author concludes that the best way to teach history is to spend most class time on the lives of historical figures and very little time on dates and statistics.
Why?
Because most students are bored by history courses as they’re usually taught. The usual way is to spend a large amount of time on dates and statistics.
Why?
Because most students are bored by history courses as they’re usually taught. The usual way is to spend a large amount of time on dates and statistics.
Notable Assumptions
The author assumes that spending most class time on recounting the lives of historical figures is NOT just as boring as spending a large amount of time on dates and statistics.
Also, the author assumes that boring students is something that detracts from the effectiveness of teaching history.
Also, the author assumes that boring students is something that detracts from the effectiveness of teaching history.
A
One should avoid boring one’s students when teaching a history course.
Necessary, because if it weren’t true, then the fact the current method of teaching history is boring wouldn’t constitute a reason a different way would be better.
B
It is not incompatible with the attainable goals of teaching history to spend very little class time on dates and statistics.
Necessary, because if it IS incompatible with the attainable goals of teaching history to spend little class time on dates and statistics, then the author’s proposed “best way” to teach wouldn’t be the best way to teach history.
C
It is possible to recount the lives of historical figures without referring to dates and statistics.
Not necessary, because the author doesn’t conclude that the best way to teach history is to completely avoid referring to dates and statistics. The conclusion is just that the best way involves spending “very little” time on dates and statistics.
D
It is compatible with the attainable goals of teaching history to spend most class time recounting the lives of historical figures.
Necessary, because if the author’s proposed method of teaching history is NOT compatible with the attainable goals of teaching history, then the method would not constitute the best way of teaching history.
E
Students are more bored by history courses as they are usually taught than they would be by courses that spend most class time recounting the lives of historical figures.
Necessary, because if students are NOT more bored by the usual method than they would be by the author’s proposed method, then the premise no longer provides a reason to think that the proposed method is better. What the author proposes would be just as boring.
Summarize Argument
The author concludes that Ziegler was insane at the time he fired the shot. This is based on the fact that the people accusing Ziegler of a crime submitted no evidence that Ziegler was sane at the time of the shot. They’ve only submitted evidence Ziegler was sane after the shot.
Identify and Describe Flaw
The author overlooks the fact that there’s evidence Ziegler was sane after the shot constitutes evidence that Ziegler was sane at the time of the shot, too. In addition, the author overlooks the fact that, even if there was a failure to submit evidence of Ziegler’s sanity at the time of the shot, that doesn’t prove Ziegler was insane at the time. Absence of evidence for a particular proposition (that Ziegler was sane at the time of the shot) does not constitute evidence against that proposition.
A
It presumes that being a well-educated professional is relevant to being guilty or innocent.
The author does not offer the claim about Ziegler’s consulting work as evidence Ziegler is innocent. So, the author does not assume that this consulting work is relevant to being guilty or innocent.
B
It concludes on the basis of evidence against Ziegler’s being sane that there is a lack of evidence for Ziegler’s being sane.
The argument is not based on evidence against Ziegler’s being sane. It’s based on the claim that there’s a lack of evidence that Ziegler was sane. Also, the argument does not conclude that there’s a lack of evidence of Ziegler’s sanity. It concludes that Ziegler was insane.
C
It fails to consider that Ziegler might have been insane when he worked as a consultant.
The author concludes that Ziegler was insane at the time of the shot. If he was also insane when he worked as a consultant, that doesn’t suggest Ziegler might have been sane at the time of the shot. So, the possibility described by (C) does not undermine the author’s reasoning.
D
It presumes that whether one is sane is relevant to whether one is morally responsible for one’s actions.
Moral responsibility has nothing to do with the argument. The author’s conclusion is that Ziegler was insane at the time he fired the shot. The conclusion is not that Ziegler shouldn’t be held morally responsible.
E
It fails to consider the possibility that Ziegler’s being sane after the shooting is an indication that he was sane at the time of the shooting.
The accusers have submitted evidence that Ziegler was sane after the shot. If this constitutes evidence that Ziegler was sane at the time of the shot, then the author’s conclusion doesn’t follow from the premises.
Summarize Argument
The argument concludes that it’s safe to assume that either underinflating or overinflating tires damages the tires. Why? Because no one has proven that underinflation or overinflation don’t damage tires.
Identify and Describe Flaw
This is a “lack of support vs. false conclusion” flaw, where a position is taken to be false just because no one has proved that it’s true. Specifically, the argument rejects the possibility that underinflation and overinflation are harmless, just because that possibility hasn’t been proven.
A
The argument assumes what it is attempting to demonstrate.
The argument does not assume that underinflation and overinflation damage tires. There is support offered, even if that support is weak.
B
The argument overlooks that what is not in principle susceptible to proof might be false.
There isn’t anything in the argument that’s “not susceptible to proof”. No one is claiming that it’s impossible to prove whether underinflation and overinflation are harmless to tires, just that it hasn’t been proven yet.
C
The argument fails to specify how it is that underinflation or overinflation harms tire tread.
The mechanism of how tire tread might be harmed isn’t relevant to the question of whether it’s safe to assume that the tire tread will be harmed, just because no one has proven that it won’t be harmed.
D
The argument rejects the possibility that what has not been proven is nevertheless true.
The argument rejects the possibility that it might be true that underinflation and overinflation don’t damage tires, even though it hasn’t been proven. This possibility undermines the idea that it’s “safe to assume” that the tires will be damaged.
E
The argument fails to precisely define the terms “underinflation” and “overinflation.”
The exact definition of what counts as an underinflated or overinflated tire is irrelevant to whether or not those conditions are likely to damage tires, based on the fact that they haven’t been proven not to damage tires.
Summary
When there’s at least one issue important to Kay, then it’s acceptable for her to vote for a person with whom she disagrees on an important issue IF she disagrees with every other candidate on a greater number of important issues. If she does not disagree with every other candidate on a greater number of important issues, she cannot vote for a person with whom she disagrees about an important issue. In the upcoming election, the three candidates are L, M, and N. There’s only 1 issue important to Kay. Kay agrees with M on that issue, but she disagrees with N and L on that issue.
Notable Valid Inferences
The question stem asks us to draw an inference about "any" election. So we should pick an answer that logically follows from one of the principles. The details about the upcoming mayoral election aren't relevant to this question stem.
A
If there are no issues important to her, it is unacceptable for her to vote for any candidate in the election.
Could be false. We don’t know what is acceptable or unacceptable when there are no issues important to Kay.
B
If she agrees with each of the candidates on most of the issues important to her, it is unacceptable for her to vote for any candidate in the election.
Could be false. It’s acceptable for her to vote for one of the candidates if she disagrees with all the other candidates on a greater number of important issues. Maybe she agrees with one cand. on 80% of imp. issues, but with the other candidates only on 70%.
C
If she agrees with a particular candidate on only one issue important to her, it is unacceptable for her to vote for that candidate.
Could be false. It’s acceptable for her to vote for that candidate if she disagrees with each of the other candidates on a greater number of important issues. She might disagree with the other candidates on every issue, for example.
D
If she disagrees with each of the candidates on exactly three issues important to her, it is unacceptable for her to vote for any candidate in the election.
Must be true. If she doesn’t disagree with each of the other candidates on a greater number of important issues, it’s unacceptable for her to vote for a candidate with whom she disagrees on an important issue. Here, she disagrees with each candidate on the same # of imp. issues.
E
If there are more issues important to her on which she disagrees with a particular candidate than there are such issues on which she agrees with that candidate, it is unacceptable for her to vote for that candidate.
Could be false. It’s acceptable for her to vote for that candidate if she disagrees with each other candidate on a greater number of important issues. She might disagree with one candidate on 55% of imp. issues, but disagree with everyone else on 70%, for example.