Summarize Argument
The resident concludes that if all remaining lead paint is eliminated from homes in the area, child lead poisoning will be eradicated. This is based on the observation that childhood lead poisoning has declined since gasoline and paint stopped being made with lead. However, there is still lead paint in some homes.
Identify and Describe Flaw
The resident claims that the elimination of lead paint from homes will completely eradicate childhood lead poisoning in the area. This overlooks the possibility that other sources of lead could be present. Those sources could continue to contribute to lead poisoning, even if lead paint in houses is eliminated.
A
relies on statistical claims that are likely to be unreliable
There’s no reason to believe that the statistical claims used in the argument are unreliable.
B
relies on an assumption that is tantamount to assuming that the conclusion is true
There isn’t any assumption in the argument that assumes the conclusion is true.
C
fails to consider that there may be other significant sources of lead in the area’s environment
The resident overlooks the possibility that other major lead sources could still cause childhood lead poisoning in the area. However, if that were true, it would severely undermine the resident’s conclusion.
D
takes for granted that lead paint in homes can be eliminated economically
The argument doesn’t make any claims about whether lead paint in homes can be eliminated economically. The argument only makes claims about what would happen if it were eliminated.
E
takes for granted that children reside in all of the homes in the area that contain lead paint
The argument doesn’t take for granted that children reside in all of the homes with lead paint, only that there are at least some children residing in homes with lead paint.
Summary
The stimulus can be diagrammed as follows:
Notable Valid Inferences
If exact caffeine content were listed on soft drink labels, some people would limit their caffeine intake.
If it became easier for people to limit their caffeine intake, some people’s health would improve.
If exact caffeine content were listed on soft drink labels, some people’s health would improve.
If it became easier for people to limit their caffeine intake, some people’s health would improve.
If exact caffeine content were listed on soft drink labels, some people’s health would improve.
A
The health of at least some people would improve if exact caffeine content were listed on soft-drink labels.
Must be true. As shown in the stimulus diagram, if caffeine content is listed, it’s easier to limit intake; if it it’s easier to limit intake, some people would; if people do, their health improves. So “list caffeine content” is a sufficient condition for “improve their health”!
B
Many people will be unable to limit their caffeine intake if exact caffeine content is not listed on soft-drink labels.
Could be false. Answer choice (B) has a negation issue: it takes a statement from the stimulus (list caffeine content → easier to limit) and negates the sufficient condition. We can’t draw conclusions from negated sufficient conditions—that’s like taking half the contrapositive!
C
Many people will find it difficult to eliminate their caffeine intake if they have to guess exactly how much caffeine is in their soft drinks.
Could be false. The stimulus doesn’t tell us anything about what happens if people have to guess how much caffeine is in their soft drinks; we only have information about what happens if the caffeine content is listed.
D
People who wish to eliminate, rather than simply limit, their caffeine intake would benefit if exact caffeine content were listed on soft-drink labels.
Could be false. The stimulus doesn’t tell us anything about people who wish to eliminate their caffeine intake; we only have information about some people who would limit their intake if soft drink labels listed exact content.
E
The health of at least some people would worsen if everyone knew exactly how much caffeine was in their soft drinks.
Could be false. While we know that some people’s health would improve if they could see soft drinks’ caffeine content on the label, we know nothing about people outside that group—maybe some people’s health would worsen, or maybe everyone else’ health would stay the same.
Summarize Argument: Counter-Position
The author concludes that explorers to Mars would not be unlikely to survive the trip to Mars. This is based on the fact that there would be a well-engineered backup system at every stage of the trip. In addition, at each stage of the trip, a fatal accident is unlikely if the backup system is in place.
Identify and Describe Flaw
The author overlooks the possibility that the risk of a fatal accident for the trip overall is greater than 50%, even if the risk at each individual stage is less than 50%. In other words, the author overlooks the possibility that what is true about the part (having a less than 50% chance of accident) might not be true about the overall whole.
A
infers that something is true of a whole merely from the fact that it is true of each of the parts
The argument infers that something is true of a whole (the trip will involve less than 50% chance of death) merely from the fact that it is true of each of the parts (each stage involves less than 50% chance of death).
B
infers that something cannot occur merely from the fact that it is unlikely to occur
The conclusion is not that a fatal accident “cannot” occur. The conclusion is simply that it is unlikely to happen during a trip to Mars. Also, the premises do not establish that a fatal accident is unlikely to occur. That is the author’s flawed assumption based on the premises.
C
draws a conclusion about what must be the case based on evidence about what is probably the case
The conclusion is simply that a fatal accident is unlikely to happen. Also, the premises do not establish that a fatal accident probably won’t happen on the trip. That is the flawed assumption based on the premises about each stage.
D
infers that something will work merely because it could work
The author does not infer that anything “will” (as in, with 100% certainty) work. The conclusion is simply that a fatal accident is unlikely during the trip.
E
rejects a view merely on the grounds that an inadequate argument has been made for it
The author does reject the view that people are unlikely to survive the trip, but not because of an inadequate argument in support of the view. The author’s premises involve the chance of death at each stage of the trip. This isn’t related to the weakness of an opposing argument.
Summary
The author concludes that retrospective studies can’t reliably accomplish their goal (determine causes of present characteristics) because they must use the subjects’ self-reported data.
Missing Connection
The conclusion determines that these studies aren’t reliable, but the only support for this is that they use subjects’ self-reported data. We can validly draw the conclusion if we know that self-reported data isn’t reliable.
A
Whether or not a study of human subjects can reliably determine the causes of those subjects’ present characteristics may depend at least in part on the extent to which that study uses inaccurate reports about the subjects’ pasts.
This deals with the right core elements, but isn’t strong enough. And even with a stronger rephrasing, e.g. “... subjects’ present characteristics depend on...”, it would still be wrong because 1) we were not told the reports are inaccurate, 2) we don’t know the extent.
B
A retrospective study cannot reliably determine the causes of human subjects’ present characteristics unless there exist correlations between the present characteristics of the subjects and what happened to those subjects in the past.
Irrelevant. We do not know if there are any correlations or not.
C
In studies of human subjects that attempt to find connections between subjects’ present characteristics and what happened to those subjects in the past, the subjects’ reports about their own pasts are highly susceptible to inaccuracy.
This is a direct link from retrospective studies and an unavoidable part of those studies (self-reported data) to inaccuracy. We can conclude that these studies’ determinations aren’t reliable.
D
If a study of human subjects uses only accurate reports about the subjects’ pasts, then that study can reliably determine the causes of those subjects’ present characteristics.
We are trying to conclude that the studies cannot reliably determine the cause, not that they can. Also, we don’t know if the reports are accurate or not.
E
Every scientific study in which researchers look for significant connections between the present characteristics of subjects and what happened to those subjects in the past must use the subjects’ reports about their own pasts.
The conclusion is only about retrospective studies. It isn’t about all studies that look at these connections.
Summarize Argument
It is more likely that the extra space on gigantic planes will be used for more passenger seating than shops and lounges. This is because the number of passengers flying is expected to dramatically increase, and normal-sized planes alone would not be able to accommodate all those passengers. Therefore, the extra space on gigantic planes must be utilized to carry passengers.
Identify Conclusion
The conclusion is the author’s hypothesis about what the extra space will be used for: “the additional space will more likely be used for more passenger seating.”
A
Gigantic planes currently being developed will have enough space in them to hold shops and lounges as well as passenger seating.
This is context that sets up the argument about what that extra space will actually be used for.
B
The additional space in the gigantic planes currently being developed is more likely to be filled with passenger seating than with shops and lounges.
This accurately rephrases the conclusion. The conclusion is that it is more likely that the additional space on gigantic planes will be used for passenger seating. More likely than what? The shops and lounges mentioned in the context.
C
The number of passengers flying the air-traffic system is expected to triple within 20 years.
This is support for why the extra space on gigantic planes will likely be used for passenger seating. There will be lots more passengers that need seats.
D
In 20 years, it will be impossible for airports to accommodate enough normal-sized planes to carry the number of passengers that are expected to be flying then.
This is support for why gigantic planes will likely use the extra space for seating. Regular planes alone can’t carry the passenger load because there isn’t enough space for all the planes that would be needed. Therefore, gigantic planes need to carry the extra passengers.
E
In 20 years, most airline passengers will be flying in gigantic passenger planes.
This is not contained in the stimulus. The argument is about what the space on gigantic planes will be used for, not where most passengers will be flying. We have no idea what the proportions will be.
Reporter: This means, then, that if anyone in the study had athlete’s foot that was not cured, that person did not receive medication M.
Summarize Argument
The reporter concludes that, in a study testing medications for athlete’s foot, anyone who was not cured was not given medication M. This is based on the observation that, in the study, everyone whose athlete’s foot was cured received medication M.
Identify and Describe Flaw
This is a cookie-cutter flaw: confusing sufficient and necessary conditions. In the study, everyone whose athlete’s foot was cured received medication M, making medication M necessary to have been cured in this study. However, that doesn’t mean medication M is sufficient to cure every case that it was used to treat. In other words, it’s possible that not everyone who received medication M was cured.
A
The reporter concludes from evidence showing only that M can cure athlete’s foot that M always cures athlete’s foot.
The argument confuses sufficient and necessary conditions. Only M cures athlete’s foot, making it necessary for curing athlete’s foot in the study. However, that doesn’t mean it’s sufficient to always cure athlete’s foot.
B
The reporter illicitly draws a conclusion about the population as a whole on the basis of a study conducted only on a sample of the population.
The reporter only draws a conclusion about the study, not the population as a whole.
C
The reporter presumes, without providing justification, that medications M and N are available to people who have athlete’s foot but did not participate in the study.
The reporter doesn’t make any claims about the availability of the medications, only their effects on athlete’s foot in the study.
D
The reporter fails to allow for the possibility that athlete’s foot may be cured even if neither of the two medications studied is taken.
The reporter is only drawing a conclusion about the efficacy of medication M based on the study, and doesn’t need to account for the possibility that athlete’s foot could be cured in other ways.
E
The reporter presumes, without providing justification, that there is no sizeable subgroup of people whose athlete’s foot will be cured only if they do not take medication M.
The reporter is only discussing the study, where every participant whose athlete’s foot was cured had received M. The possibility of this kind of subgroup is irrelevant to M being necessary to cure athlete’s foot in the study.