Summary
The Biocarb Company’s president concludes that a new sterilization plant will not cause pollution. Why not? Because the medical waste treated at the plant will be sterilized by exposure to superheated steam until it is cleaner than food could ever be.
Notable Assumptions
The president broadly assumes that there won’t be any potential sources of pollution from operating the plant, other than waste which has been fully sterilized. For example, there won’t be byproducts from the process of running the plant’s autoclave which could constitute pollution.
The president also assumes that the waste won’t pose a risk of pollution even after sterilization, for example if it contains plastics or heavy metals that might be harmful despite being free of pathogen contamination.
The president also assumes that the waste won’t pose a risk of pollution even after sterilization, for example if it contains plastics or heavy metals that might be harmful despite being free of pathogen contamination.
A
Environmental activists believe that waste treated with steam will not pollute.
Whether or not the president’s argument holds up doesn’t depend on what the environmental activists believe, so this is not necessary.
B
Handling of the waste before treatment in the proposed facility will not pose a threat of pollution to the area.
This falls under the broad assumption that there aren’t potential pollution risks other than the fully sterilized waste. If this were negated, and the handling of unsterilized waste posed a threat of pollution, the premises about sterilization couldn’t support the conclusion.
C
Fear of pollution is the only argument against construction of an autoclave facility for medical waste.
The argument isn’t about the overall cost-benefit of the factory, just about whether it poses a pollution risk, so the presence or absence of other arguments is irrelevant.
D
No others besides environmental activists are concerned about pollution hazards that can result from processing medical waste.
Any beliefs that people do or don’t have about the factory wouldn’t affect the president’s argument, which is about material reality, so this is not necessary either way.
E
Treatment by superheated steam represents the surest method of sterilization.
As long as the waste will reliably be sterilized, it doesn’t matter whether steam treatment is the surest method or just a very, very sure method. In other words, this isn’t necessary to assume.
Summary
The author explains that most ant species use pheromone trails to find the way between their nest and food sources. However, the power of pheromones is limited: they are destroyed by temperatures over 45 degrees Celsius (113 Fahrenheit). Incidentally, afternoons in the Sahara Desert usually rise above this temperature.
Strongly Supported Conclusions
The stimulus strongly supports these inferences:
Pheromone trails would be destroyed by heat during most Sahara afternoons.
Ants are not able to navigate using pheromone trails when the temperature is above 45 Celsius/113 Fahrenheit.
If any ants forage in the Sahara in the afternoon, for the most part they can’t use pheromones to navigate during that time.
Pheromone trails would be destroyed by heat during most Sahara afternoons.
Ants are not able to navigate using pheromone trails when the temperature is above 45 Celsius/113 Fahrenheit.
If any ants forage in the Sahara in the afternoon, for the most part they can’t use pheromones to navigate during that time.
A
Most ants forage for food either only in the morning or only during the night.
This is not supported. The stimulus doesn’t talk directly about when ants forage. We also can’t draw a conclusion from temperatures, because we only know about Sahara afternoon temperatures. When and where is it cool enough for pheromones? We have no clue.
B
Most ants that do not use pheromones to mark the paths they take between their nest and food live in the Sahara Desert.
This is not supported. The stimulus doesn’t indicate if any ants live in the Sahara at all, much less that most non-pheromone-using ants do.
C
If any ants live in the Sahara Desert and forage for food at no time but in the afternoon, those ants generally do not use pheromones to guide themselves between food and their nest.
This is strongly supported. We know that ants can’t use pheromones to navigate during most Sahara afternoons. This means that if any ants only forage during Sahara afternoons, they generally can’t—so don’t—navigate using pheromones.
D
If any ants do not use pheromones to navigate between food and their nest, those ants use a different substance that does not evaporate in temperatures above 45 degrees Celsius.
This is not supported. The author never suggests how ants might navigate other than by using pheromones. We have no idea if it’s a different substance or some other method altogether.
E
If any Saharan ants forage for food in the afternoon, those ants forage for food less efficiently when temperatures are above 45 degrees Celsius than they do when temperatures are lower.
This is not supported. It might seem like not being able to use pheromones in high temperatures would lead to less-efficient foraging, but we don’t know about other ways ants could navigate. Maybe there are equally or more-efficient methods than pheromones.
Summary
The author concludes that at most 25% of the films released in 1992 were based on books published in 1991. His reasoning is that 25% of the films released in 1992 were based on novels published in 1991.
Missing Connection
The author’s conclusion is about books, but his premise is about novels. What if there were movies based on books (e.g. biographies) that aren’t novels? We need to close this gap in the argument. We could do so by adding the assumption that all movies released in 1992 that were based on 1991 books were based on novels.
A
None of the scripts used in films released in 1992 were written by professional novelists.
This is irrelevant, because the conclusion is about the source material of the films (novels vs. other kinds of books), not the professional background of the screenwriters.
B
None of the films released in country Z in 1992 were based on books other than novels.
This is saying that, if a film based on a book was released in 1992, then it was based on a novel. If so, the 25% of 1992 films based on 1991 novels are the only films based on 1991 books. And the conclusion that 25% is the max percentage of such films is guaranteed.
C
None of the books that were published in country Z in 1992 were based on plots of films released in 1991.
This doesn’t close the gap in the argument: there could still be 1992 films based on 1991 books that aren’t novels. And thus the percentage of 1992 films based on 1991 books could be higher than 25%.
D
Some of the films released in country Z in 1992 were based on older films that had been released for the first time many years earlier.
This doesn’t close the gap in the argument: there could still be 1992 films based on 1991 books that aren’t novels. And thus the percentage of 1992 films based on 1991 books could be higher than 25%.
E
Some of the films released in 1991 in country Z were based on novels that were published in 1991.
The conclusion is about 1992 films, so 1991 films are irrelevant.
Summarize Argument
The author concludes that candidates for national political office should begin their speeches by briefly arguing against their own position before giving reasons why their position should in fact be accepted. As evidence, she claims that the technique is effective since it makes the speaker look fair-minded and trustworthy.
Notable Assumptions
The author assumes that candidates should do what audiences find generally most effective in a speech. This means that the author doesn’t believe that candidates’ speeches differ from other sorts of speeches, at least not to an extent that the technique wouldn’t work.
A
Political candidates typically have no control over which excerpts from their speeches will be reported by the news media.
While a candidate holds position A, the news media simply shows clips of them arguing against that same position. This isn’t a good look for a candidates, and seriously weakens the efficacy of this technique.
B
Many people do not find arguments made by politicians convincing, since the arguments are often one-sided or oversimplify the issues.
If anything, this strengthens the author’s position. If people find politicians’ arguments one-sided, then this technique would presumably mitigate that problem.
C
People decide which political candidate to vote for more on the basis of their opinions of the candidate’s character than on the exact positions of the candidate.
While people care more about the candidate’s character than their positions, the positions may still matter. And the technique the author recommends might then still be effective.
D
People regard a political candidate more favorably if they think that the candidate respects an opponent’s position even while disagreeing with it.
This seems to support the author’s argument. If people think being fair and even-handed is a good quality in a candidate, than the recommended technique would be useful.
E
Political candidates have to address audiences of many different sizes and at many different locations in the course of a political campaign.
We have no idea how the technique in question works on different audiences. We know that, in general, it’s effective. We need something that weakens the idea politicians should start using it.
Summarize Argument: Phenomenon-Hypothesis
The author concludes that there must be at least one undiscovered planet in our solar system. This is because measurements show that Uranus is being pulled away from the Sun by some force, and the planets further from the Sun than Uranus are too small to provide that force.
Notable Assumptions
The author assumes that a planet must be providing the force pulling Uranus away from the Sun. This means he doesn’t believe the force could from any other celestial object. The author also assumes that Neptune and Pluto couldn’t together provide the necessary force to pull Uranus away from the Sun.
A
Pluto was not discovered until 1930.
It doesn’t matter when Pluto was discovered. We need to weaken the idea that there findings around Uranus mean there’s an undiscovered planet in our solar system.
B
There is a belt of comets beyond the orbit of Pluto with powerful gravitational pull.
Even though Pluto and Neptune lack the mass to pull Uranus away from the Sun, there’s a belt of comets behind Pluto fully capable of doing so. This suggests that the author’s “another planet” hypothesis has overlooked an important fact.
C
Neither Neptune nor Pluto is as massive as Uranus.
We already know Neptune and Pluto don’t have the mass to pull Uranus away from the Sun. This doesn’t challenge anything in the author’s argument.
D
The force the Sun exerts on Uranus is weaker than the force it exerts on the inner planets.
This is probably true, but it doesn’t matter. We need to challenge the “another planet” hypothesis the author arrives on.
E
Uranus’ orbit is closer to Neptune’s orbit than it is to Pluto’s.
Neither planet has the adequate mass to pull Uranus away from the Sun. This leaves the door open to the author’s hypothesis.
Summary
The argument concludes that if people modified their weight, based on their height, to fall within a standard range, they would live longer. This is supported by the claim that, according to insurance companies, people within the standard weight range for their height live longer.
Notable Assumptions
The argument uses a correlation as support to conclude that a causal relationship exists. This requires assuming that there aren’t other factors, underlying weight, that impact life expectancy and aren’t affected by a change in weight.
The argument also requires assuming that, even if a change in weight can improve life expectancy, making that change wouldn’t also involve damage to people’s health that would decrease their life expectancy.
The argument also requires assuming that, even if a change in weight can improve life expectancy, making that change wouldn’t also involve damage to people’s health that would decrease their life expectancy.
A
Some people would be unwilling to modify their weights solely to increase the general population’s overall life expectancies.
People’s willingness to modify their weight is irrelevant—the argument is only claiming that some people could improve their life expectancy by modifying their weight, not that they necessarily will.
B
Life insurance companies intended their tables to guide individuals in adjusting their weights in order to increase their life spans.
The intention that led the insurance companies to create these tables is irrelevant to their actual usefulness to guide people’s changes in weight.
C
The tables include data gathered from policyholders whose deaths resulted from accidents in addition to those whose deaths resulted from natural causes.
If anything, the data would be a more reliable indicator of how weight impacts lifespan if accidental deaths were excluded, so an assumption that accidental deaths were included is not necessary.
D
Holders of life insurance policies do not have longer overall life expectancies than the general population.
The argument merely claims that people within the standard weight range lived longer than people outside that range. This relationship could still be true even if the general population has overall shorter life expectancies, so this is not necessary.
E
People’s efforts to modify their weight to conform to a given range would not damage their health enough to decrease their overall life expectancies.
If we were to negate this—if people’s weight-modification efforts were so harmful that their lifespans decreased—that could offset any increase in lifespan. That would deeply undermine the argument, making this assumption necessary.
Summarize Argument: Phenomenon-Hypothesis
The archaeologists conclude that certain tribes had developed methods of warfare designed to maximize casualties by the late Bronze Age. Their evidence is that there are comparatively more warrior tombs from the late Bronze Age than from the early Bronze Age.
Notable Assumptions
The archaeologists assume that the tribes in question weren’t more likely to build warrior tombs in the late Bronze Age than the early Bronze Age for reasons other than the number of casualties. If these tribes only built tombs for warriors of a certain class in the early Bronze Age, then perhaps all the later tombs signify is a more egalitarian society. The archaeologists also assume that the tribes were not far more populous in the later Bronze Age than in the early Bronze Age, which would also explain the comparative number of warrior tombs.
A
A royal tomb dating to the early Bronze Age contained pottery depicting battle scenes in which warriors use spears.
We already know warriors used spears in the early Bronze Age. We’re looking for support for the claim they used different weapons in the late Bronze Age.
B
There is evidence that many buildings dating to the late Bronze Age were built by prisoners of war taken in battles between enemy tribes.
We have no idea if the same phenomenon was happening during the early Bronze Age. We can imagine the tribes took prisoners in battle during every era, simply for the labor.
C
Scenes of violent warfare, painted in bright hues, frequently appear on pottery that has been found in some early Bronze Age tombs of warriors.
We already know there was warfare in the early Bronze Age. We’re looking for support for the claim they used different weapons in the late Bronze Age.
D
Some tombs of warriors dating to the late Bronze Age contain armor and weapons that anthropologists believe were trophies taken from enemies in battle.
Were the armor and weapons advancements over what these tribes had in the early Bronze Age? We don’t know.
E
The marks on the bones of many of the late Bronze Age warriors whose tombs were excavated are consistent with the kind of wounds inflicted by arrowheads also found in many late Bronze Age settlements.
Arrowheads aren’t spears. These warriors seemed to be killed or injured in battle with new kinds of weaponry that we can be certain these tribes had in the late Bronze Age, but which they didn’t have in the early Bronze Age.
Summarize Argument: Phenomenon-Hypothesis
The author hypothesizes that owning a VCR prompts people to go to the movie theater more. She bases this on a correlation: people who tend to go to the movies more often also own a VCR.
Identify and Describe Flaw
This is a cookie-cutter “correlation does not imply causation” flaw, where the author sees a positive correlation and jumps to the conclusion that one thing causes the other, without ruling out alternative hypotheses. Specifically, she overlooks two key alternatives:
(1) The causal relationship could be reversed—maybe going to movies more causes people to get VCRs, not the other way around.
(2) Some other, underlying factor could be causing the correlation—maybe there’s something that causes people to both go to the movies and buy VCRs. (Maybe they simply like movies in general?)
A
concludes that a claim must be false because of the mere absence of evidence in its favor
The author doesn’t bring up a lack of evidence for any claims. Rather, she reaches her conclusion by presenting evidence in the form of a correlation.
B
cites, in support of the conclusion, evidence that is inconsistent with other information that is provided
The only evidence cited is a correlation between people who own VCRs and people who go to the movies more often. Everything else in the stimulus is at least consistent with this correlation being true.
C
fails to establish that the phenomena interpreted as cause and effect are not both direct effects of some other factor
This describes a key alternative hypothesis that the author ignores. She fails to establish that VCR ownership and moviegoing are not both direct effects of some other, underlying causal factor. (Maybe they’re both effects of simply liking movies in general?)
D
takes a condition that by itself guarantees the occurrence of a certain phenomenon to be a condition that therefore must be met for that phenomenon to occur
This is the cookie-cutter flaw of mistaking a sufficient condition for a necessary one. The author doesn’t make this mistake, and her argument doesn’t rely on conditional reasoning. Instead, she uses causal reasoning (and overlooks possible alternative hypotheses in the process).
E
bases a broad claim about the behavior of people in general on a comparison between two groups of people that together include only a small proportion of people overall
This is the cookie-cutter flaw of overgeneralization. But the author doesn’t generalize from a limited sample to an overly broad conclusion. Rather, she compares all people who own VCRs to all people who don’t, and so considers all people overall.
Summarize Argument: Counter-Position
This is an usual stimulus because there’s no argument. Instead, we have a claim and a reply to that claim.
Attorneys’ claim: The government destroyed evidence that would have supported the defendant.
Government’s reply: There is presently no evidence that supports the defendant.
Notable Assumptions
There are no assumptions, because there’s no argument here. But notice that the government’s reply doesn’t actually address the point made by the attorneys. The attorneys’ point is that there was once supporting evidence, before it was destroyed. But the government’s response is all about the present situation—there’s now no supporting evidence. This leaves open the possibility that the attorneys are right: the government destroyed the evidence, which is why it no longer exists.
A
It leaves open the question of whether the government had destroyed such evidence.
The government’s reply is all about the present situation—there’s now no supporting evidence. This is completely consistent with the attorneys’ claim that there was once evidence, but the government destroyed it. So the question remains: did the government destroy that evidence?
B
It establishes that the attorneys’ charge is an exaggeration.
The attorney’s charge is all about what happened in the past, while the government’s reply is solely about the present situation. So, the government’s reply does nothing to counter the attorneys’ charge.
C
It shows that the attorneys did not know whether their charge was true.
The attorney’s charge is all about what happened in the past, while the government’s reply is solely about the present situation. So, the government’s reply does nothing to counter the attorneys’ charge.
D
It demonstrates the government’s failure to search for evidence in its files.
The government’s reply might be true—there might currently be no evidence in the government’s files (or anywhere else) to support the defendant. We don’t know. So we can’t conclude that the government failed to search for evidence.
E
If true, it effectively disproves the charge made on behalf of the defendant.
The attorney’s charge is all about what happened in the past, while the government’s reply is solely about the present situation. So, even if the government’s reply is true, it does nothing to counter the attorneys’ charge.