After a major toll highway introduced a system of electronic toll paying, delays at all of its interchanges declined significantly. Travel time per car trip decreased by an average of 10 percent. Tailpipe pollution for each trip decreased commensurately. Despite this, the total air pollution from vehicles on that highway did not decrease measurably.

"Surprising" Phenomenon
The new electronic tolling system reduced delays on the highway, which decreased travel times and consequently lowered pollution levels per trip, but the total air pollution on the highway did not decrease measurably.

Objective
The correct answer will describe some other factor or phenomenon that also began when the tolls changed, but which caused increased pollution on the highway. That increase must offset the decrease from the shortened trip times, yielding essentially constant pollution levels as described in the stimulus.

A
The highway began charging higher tolls when it switched to electronic toll paying.
This would likely cause fewer people to take the highway, leading to further decreased pollution levels. We’re looking for something that would cause heightened pollution to counteract the decrease from the shortened trip times, so this does the opposite of what we need.
B
Even after the switch to electronic toll paying, there were sometimes long delays at the highway’s interchanges.
This answer doesn’t give us a factor that helps explain the constant pollution levels. The stimulus tells us that the average trip length decreased with the toll method switch, which remains true even if some trips are impacted by long delays.
C
The prospect of faster, more convenient travel induced more drivers to use the highway.
This explains why the pollution level on the highway remains the same despite the fact that the average pollution per trip went down: the shortened trip times attracted more drivers, so even though each trip produces less pollution on average, there are now more trips overall.
D
Travel time on the highway for car trips under 30 kilometers (18.6 miles) did not decrease appreciably.
Even if shorter-distance trips did not become markedly faster, we know that trips on the highway did on average. We would therefore still expect to see lowered pollution levels based on this answer and the stimulus alone, so this doesn’t help reconcile the issue at hand.
E
Some drivers did not switch to the electronic system but instead continued to use cash to pay their tolls at toll booths.
This answer doesn’t give us a factor that helps explain the constant pollution levels. The stimulus tells us that the switch to the electronic system had an impact on average trip times, whether or not every driver utilized the new system.

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Critic: The Gazette-Standard newspaper recently increased its editorial staff to avoid factual errors. But this clearly is not working. Compared to its biggest competitor, the Gazette-Standard currently runs significantly more corrections acknowledging factual errors.

Summarize Argument

The critic concludes that the Gazette-Standard’s increase in editorial staff isn’t working. His evidence is that the Gazette-Standard runs more corrections of factual errors than its competitors.

Notable Assumptions

The critic assumes that the Gazette-Standard runs more corrections of factual errors because more factual errors appear in its pages than those of competing newspapers. This means the critic doesn’t think other newspapers are making as many or more mistakes without correcting them.

A
The Gazette-Standard pays its editorial staff lower salaries than its biggest competitor pays its editorial staff.

We don’t care how much the Gazette-Standard pays its editorial staff. We have no idea how that would affect their quality of work.

B
The Gazette-Standard has been in business considerably longer than has its biggest competitor.

We don’t care how long these newspapers have been in business. We care about the recent editorial changes.

C
The Gazette-Standard more actively follows up reader complaints about errors in the paper than does its biggest competitor.

The Gazette-Standard runs more corrections because it follows up on reader complaints. We therefore can’t conclude the Gazette-Standard actually has more errors than its competitor, who may only follow up on a small portion of reader complaints.

D
The Gazette-Standard’s articles are each checked by more editors than are the articles of its biggest competitor.

If these articles are being checked by more editors, then the newspaper shouldn’t have to keep running so many corrections. This seems to support the author’s argument.

E
The increase in the Gazette-Standard’s editorial staff has been offset by a decrease in the reporting staff at the newspaper.

Less reporters doesn’t mean the newspaper will necessarily have more editorial errors. We have no idea what effect less reporters would have on the newspaper.


23 comments

In 2005, an environmental group conducted a study measuring the levels of toxic chemicals in the bodies of eleven volunteers. Scientifically valid inferences could not be drawn from the study because of the small sample size, but the results were interesting nonetheless. Among the subjects tested, younger subjects showed much lower levels of PCBs—toxic chemicals that were banned in the 1970s. This proves that the regulation banning PCBs was effective in reducing human exposure to those chemicals.

Summarize Argument
The author concludes that the regulation banning PCBs was effective in reducing human exposure to those chemicals. This is based on a study that measured the levels of toxic chemicals in the bodies of 11 volunteers. Although scientifically valid inferences can’t be drawn from the study, the author states that the study showed that younger people showed much lower levels of PCBs than older people. PCBs were banned in the 1970s.

Identify and Describe Flaw
Despite acknowledging that we can’t draw scientifically valid inferences from the study due to its small sample size, the author proceeds to draw a conclusion based on that study. The author contradicts himself.

A
takes an inconsistent stance regarding the status of the inferences that can be drawn from the study
The author’s stance regarding whether we can draw valid inferences from the study is inconsistent. The author first says we can’t. But the author then tries to draw a conclusion.
B
overlooks the possibility that two or more chemicals produce the same effects
This possibility doesn’t undermine the argument, because the reasoning doesn’t involve the effects of chemicals. The argument is based on a study that shows younger people in the study had lower levels of PCBs. The effects of PCBs, however, are not at issue.
C
concludes that a generalization has been proven true merely on the grounds that it has not been proven false
The author doesn’t reach the conclusion on the basis of a claim that nobody has proven that the regulation banning PCBs wasn’t effective. The conclusion is based on a study.
D
takes something to be the cause of a reduction when it could have been an effect of that reduction
It doesn’t make sense to think that a reduction in PCBs could cause the regulations banning PCBs. Not every cause and effect relationship can be reversed.
E
does not consider the possibility that PCBs have detrimental effects on human health several years after exposure
This possibility doesn’t undermine the argument, because the reasoning doesn’t involve the effects of chemicals. The argument is based on a study that shows younger people in the study had lower levels of PCBs. The effects of PCBs, however, are not at issue.

11 comments