Summary
The author concludes that if there’s no methane on Planet 253, then there is no life on Planet 253. Why? Because if there is no methane, then there are no microbes.
Missing Connection
We know that if there’s no methane, there’s no microbes. But how does this imply that if there’s no methane, there’s no LIFE? “No life” is a new concept in the conclusion. So, at a minimum, the correct answer must tell us what is sufficient to lead to “no life,” or what is required in order to have “life.”
To go further, we can anticipate a more specific connection. We already know from the premise that “no methane” implies “no microbes.” To get to “no life,” we just want to establish that “no microbes” implies “no life.” In other words, that life requires microbes.
To go further, we can anticipate a more specific connection. We already know from the premise that “no methane” implies “no microbes.” To get to “no life,” we just want to establish that “no microbes” implies “no life.” In other words, that life requires microbes.
A
There is, in fact, no methane on Planet 253.
The conclusion is conditioned on the hypothetical that there is no methane on Planet 253. Whether this hypothetical is true doesn’t prove the conclusion, because the conclusion already presumes that it’s true for the purpose of the argument.
B
If methane exists on Planet 253 then we would be able to detect its presence.
(B) doesn’t establish what is sufficient to lead to “no life.” Since neither this answer nor the premises establish what leads to “no life,” (B) cannot make the argument valid.
C
If there is no methane currently on Planet 253 then there has never been methane on Planet 253.
(C) doesn’t establish what is sufficient to lead to “no life.” Since neither this answer nor the premises establish what leads to “no life,” (C) cannot make the argument valid.
D
If there are no microbes on Planet 253 then there is no life on Planet 253.
We know that if there’s no methane on Planet 253, there’s no microbes on Planet 253. According to (D), that allows us to conclude there is no life on Planet 253, if there’s no methane.
E
If there is methane on Planet 253 then there must be life on Planet 253.
(E) allows us to reach a conclusion that there IS life on Planet 253. But we want to establish that there is NO life on the planet. (E) is essentially a version of the conclusion that confuses sufficiency and necessity.
Summary
Commercial fishing equipment became more technically sophisticated from 1960 through 2010.
The commercial fishing industry has been able to harvest a greater percentage of the total amount of fish in the ocean by weight each succeeding year from 1960 through 2010.
The industry’s harvest by weight increased from 1960 until 1995,
The industry’s harvest by weight did not increase from 1995 through 2010.
Notable Valid Inferences
From 1995 through 2010, each year, the industry harvested a greater percentage of the total amount of fish in the ocean (by weight), but the amount of fish harvested by weight did not increase. This means that the total amount of fish by weight in the ocean decreased each year from 1995 through 2010.
A
After 1995, the number of fish harvested each year by the commercial fishing industry increased, but the average weight of each fish harvested decreased.
Could be false. All of the information in the stimulus is about fish by weight; we have no information about the number of fish harvested or the average weight of each fish.
B
After 2010, improvements in commercial fishing equipment did not enable the fishing industry to harvest a greater percentage of the total amount of fish, by weight, in the world’s oceans.
Could be false. The stimulus does not provide information about what happened technologically after 2010.
C
The total amount of fish, by weight, in the world’s oceans decreased during the period from 1995 to 2010.
Must be true. In order for it to be true that the industry harvested a greater percentage of the total weight of fish in the ocean, but the amount of fish harvested by weight did not increase, it must be the case that the total amount of fish by weight in the ocean decreased.
D
The commercial fishing industry’s harvest, by weight, was significantly lower in 2010 than it was in 1995.
Could be false. We know that the commercial fishing industry’s harvest by weight was not higher in 2010 than it was in 1995, but it could be true that the harvest was the same or only slightly lower.
E
No significant improvements in commercial fishing equipment occurred before 1960.
Could be false. We know that the technical sophistication increased steadily from 1960 through 2010; we don’t have any information about the equipment before 1960.
Summarize Argument: Phenomenon-Hypothesis
The author hypothesizes that experiencing a traumatic event can affect how much cortisol one produces in response to stress. This is based on the fact that people who have experienced a traumatic event but don’t develop PTSD tend to produce higher levels of cortisol in times of stress than do people who haven’t experienced traumatic events.
Notable Assumptions
The author assumes that people who have experienced traumatic events without developing PTSD are representative of people who have experienced traumatic events generally (i.e. including those who did develop PTSD) with respect to the amount of cortisol produced in times of stress. The author also assumes that there isn’t another explanation for the correlation observed between cortisol amounts produced and experiencing a traumatic event without PTSD.
A
Medical conditions sometimes affect how much cortisol people who have not experienced a traumatic event produce in response to stress.
“Sometimes” could just be a single occasion. We don’t have any reason to think these conditions occur often enough to explain the lower average cortisol production of the group of people who haven’t experienced traumatic events.
B
Producing more cortisol than average in response to stress helps prevent a person from developing PTSD as a result of experiencing a traumatic event.
This raises the potential of reverse causation. Maybe people who start off producing more cortisol are more likely to avoid PTSD after trauma. This might be explain why the trauma + no PTSD group has higher cortisol production than the group that didn’t experience trauma.
C
People experiencing a traumatic event produce more cortisol than they would under less severe instances of stress.
If anything, this might support the alleged connection between traumatic events and producing more cortisol in times of stress.
D
Many effective treatments for PTSD are designed to reduce how much cortisol those with PTSD produce when exposed to stress.
The comparison in the stimulus involves people who don’t have PTSD. So they wouldn’t be taking the medications described in (D).
E
Experiencing a traumatic event can damage the gland that produces cortisol, resulting in that gland producing more cortisol.
This strengthens the argument by providing a causal mechanism for how experiencing trauma might lead to more cortisol production in times of stress.
Answers (A), (B), and (D) would have been better (I dare say right) if they said something like:
Parents should encourage children to do something only if it doesn't make unhappy.
Parents should encourage children to do only those things that don't lead them to develop a sense of resentment.
Economist: Machinery firms in this country argue that in order to grow big enough to compete successfully with foreign rivals, the protection that they have been receiving from foreign competition must be extended for several more years. Yet these firms have been receiving protection from foreign competition for the last ten years. If it were possible for protection from foreign competition to enable this country’s machinery firms to grow big enough to compete successfully with foreign rivals, ten years would be a sufficient time frame for this to happen.
Summary
If protection from foreign competition were possible in order to allow domestic machinery firms to successfully compete with foreign machinery firms, ten years would be a sufficient timeframe for this purpose. However domestic machinery firms have had protection from foreign competition for the last ten years, and these firms claim that this protection must be extended for several more years.
Strongly Supported Conclusions
It is not possible that protection from foreign competition will allow domestic machinery firms to grow big enough to compete with foreign machinery firms.
A
Protection from foreign competition rarely if ever enables firms to grow big enough to compete with foreign rivals.
The Economist’s argument is limited to machinery firms in the Economist’s country. We don’t know whether protection “rarely” allows firms to grow big enough generally. We only know that protection does not allow domestic machinery firms to grow big enough.
B
Ten years is a sufficient time frame for assessing the success of any economic policy.
We don’t know if ten years is sufficient for evaluating any and every economic policy. We only know ten years is sufficient for evaluating one economic policy that applies to domestic machinery firms.
C
None of the machinery firms in the economist’s country has grown significantly over the last ten years.
We don’t know whether or not any machinery firm in the economist’s county has grown “significantly.” We only know that these machinery firms haven’t grown big enough to compete with foreign machinery firms.
D
Most of the machinery firms in the economist’s country will go out of business unless they are protected from foreign competition.
We don’t know whether any of the machinery firms in the Economist’s country will go out of business if these firms are not protected from foreign competition.
E
Protection from foreign competition will not enable machinery firms in the economist’s country to grow big enough to take on foreign rivals.
It is not possible that protection from foreign competition will allow domestic machinery firms to grow big enough to compete since these firms have already been receiving protection for ten years.
Summarize Argument
The author concludes that crime isn’t adversely affecting his business by reducing the number of people willing to shop at his store. He supports this main conclusion with the subsidiary conclusion that his customers aren’t worried about crime in the neighborhood. This sub-conclusion is supported by the fact that people he talks to in his store say that they’re not worried about crime.
Identify and Describe Flaw
The author overlooks the fact that the people in his store who aren’t worried about crime might not be representative of the people who might want to shop at the store. Other people who aren’t shopping at the store might be worried about crime.
A
infers that something is not the case on the grounds that there is only a small amount of evidence for its being the case
The conclusion is not based on a claim that there’s only a small amount of evidence that crime is reducing the number of people willing to shop at the store. The conclusion is based on the conversations the author has had with people who say they aren’t worried about crime.
B
appeals to personal opinion to establish a factual claim
There’s nothing flawed about relying on what people say about their fear of crime to establish whether those people are afraid of crime. This isn’t a case of using personal opinion inappropriately to establish a factual matter.
C
generalizes about the whole neighborhood based on the case of one store
The conclusion is just about the author’s store. It’s not about the whole neighborhood.
D
draws a conclusion on the basis of a biased sample
The conclusion is based on the sample of people who shop at his store. They are not necessarily representative of people generally. People who aren’t shopping at the store might be too afraid to shop there, whereas the people who do shop there are the ones who aren’t afraid.
E
fails to consider that crime might affect the neighborhood negatively without affecting businesses negatively
The conclusion is just about whether crime is reducing the number of people shopping at the store. Whether the neighborhood is affected in other weighs is irrelevant.
Summary
The author concludes that all serious novelists are NOT motivated primarily by desire to make money. This is based on the fact taht all serious novelists care about literary style.
Missing Connection
We’re trying to conclude that serious novelists are NOT motivated primarily by desire to make money. But we don’t have any premise that establishes when someone is not motivated primarily by desire to make money. So, at a minimum, the correct answer must tell us what leads to “not motivated primarily by desire to make money.”
To go further, we can anticipate a more specific connection between the premise and conclusion. We know from the premise that serious novelists care about literary style. To make the argument valid, we want to get from “care about literary style” to “not motivated primarily by desire to make money.”
To go further, we can anticipate a more specific connection between the premise and conclusion. We know from the premise that serious novelists care about literary style. To make the argument valid, we want to get from “care about literary style” to “not motivated primarily by desire to make money.”
A
No novel written by a serious novelist in fact appeals to the general public.
(A) doesn’t establish anything about a novelists’ motivations. Since neither this answer nor the premise establishes anything about a novelists’ motivations, it cannot make the argument valid.
B
No novelist who cares about literary style is motivated primarily by the desire to make money.
(B) establishes that if a novelist cares about literary style, then they are NOT motivated primarily by desire to make money. (”No A is B” = “If A, then Not B.”) Since we know that serious novelists care about literary style, (B) allows us to conclude that serious novelists aren’t motivated primarily by making money.
C
No novelist whose novels exhibit good literary style is motivated primarily by the desire to make money.
We don’t know whether serious novelists’ works “exhibit good literary style.” We know that the noveslists care about style, but that doesn’t imply their works have good literary style. So (C) doesn’t interact with the premise and cannot make the argument valid.
D
Any novelist who is motivated primarily by the desire to make money writes novels that in fact appeal to the general public.
We don’t know that serious novelists’ works are novels that do NOT appeal to the general public. So we can’t use (D) to establish that serious novelists aren’t motivated primarily by desire to make money.
E
Any novel that in fact appeals to the general public was written by a novelist motivated primarily by the desire to make money.
We’re trying to prove that serious novelists are NOT motivated primarily by desire to make money. (E) allows us to reach a conclusion that someone IS motivated primarily to make money.
Summarize Argument
The author concludes that new, more complicated computer control systems for controlling air bags will probably increase the likelihood of accidental air bag inflation. This is because the new systems have more ways to fail than the older air bag control systems.
Identify and Describe Flaw
The author assumes that have a greater number of ways to fail implies a greater overall chance of failing. This doesn’t have to be true. Maybe, for example, there are now twice as many ways to fail. But each of those ways might have a tiny chance of occurring, such that the overall chance of failure is not necessarily higher than the chance that older systems would fail. Older systems might have had just one or two ways to fail, but each way could have had a very high chance of occurring.
A
It fails to address adequately the possibility that the likelihood of a system’s failing need not increase with the number of ways in which it can fail.
This possibility points out why the conclusion doesn’t follow. The chance a system fails does not have to increase just because the number of ways to fail increases. The overall chance of failure might go down, even if the number of ways to fail goes up.
B
It takes for granted that any failure in an air bag’s computer control system will cause that air bag to inflate accidentally.
The author believes a more complex system involving more ways of failure will involve more instances of air bag inflation. But this doesn’t mean the author thinks every failure involves air bag inflation. There can be some failures that don’t lead to inflated air bags.
C
It fails to address adequately the possibility that air bags may often accidentally inflate even when their computer control systems do not fail.
This possibility doesn’t undermine the argument. There can be accidental inflation even when systems don’t fail. That doesn’t undermine the belief that a greater number of ways to fail implies a greater chance of accidental air bag inflation.
D
It overlooks the possibility that, even if the new computer control systems exacerbate the problems with accidental air bag inflation, they may have advantages that outweigh this disadvantage.
The author’s conclusion is not about whether we should implement the new control systems. So whether there are advantages or disadvantages to the new system have no bearing on whether the new system is more likely to lead to accidental air bag inflation.
E
It overlooks the possibility that, even if air bags occasionally cause accidental injuries, they may nonetheless be responsible for preventing many more injuries than they cause.
This possibility doesn’t undermine the argument. Whether airbags prevent more injuries than they cause doesn’t affect whether there will be more accidental air bag inflation with the more complex system.
Summarize Argument
The author concludes that environmental factors have little effect on whether a teenager will participate in sports. This is based on the fact that it’s common for one teenager in a family to participate in sports, but for the other teenagers in the same family to avoid sports. In addition, school programs that try to get inactive teenagers to participate in sports are usually ineffective.
Notable Assumptions
The author assumes that evidence of the ineffectiveness of certain environmental factors, such as family and school environment, shows that other environmental factors are similarly ineffective. The author also assumes that the family environment is generally similar from one teen to another within the same family.
A
Athletic ability varies, even among siblings, and teenagers who have demonstrable athletic ability are more likely than those who do not to participate in sports.
This strengthens the argument by suggesting difference in athletic ability (which is not an environmental factor) might be the predominant cause of differences in sports participation among members of the same family.
B
Some teenagers, even those in schools that do not have any sports programs, are more enthusiastic about participating in sports than their parents are.
Comparisons of enthusiasm between teens and parents don’t have any clear impact. If anything, (B) might strengthen by showing that teens’ participation is not influenced much by parents’ lower enthuasiasm.
C
Adults’ enthusiasm for participating in sports generally is directly proportional to the extent to which they participated in sports when they were younger.
This tells us about how adults’ enthusiasm relates to the same adults’ enthusiasm when they were younger. But this doesn’t reveal anything about what might have caused their enthusiasm when they were younger.
D
The proportion of teenagers who participate in sports varies greatly from society to society and from decade to decade.
Different societies/decades involve different environments (ex. think about cultures in different countries and times). If environment had little impact, we’d expect sports participation not to vary widely. But it does, suggesting environment has more than little impact.
E
School programs designed to encourage inactive teenagers to participate in sports widely vary in success, with only a few being highly successful.
If anything, this might strengthen the argument by providing additional evidence to question the effectiveness of programs designed to get teens to participate in sports. If only a few are highly successful, maybe it’s just coincidence. The program might not be the cause.