Weaken
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LSAT Logical Reasoning › Weaken
Which one of the following, if true, most seriously weakens the argument?
The decline in collisions was accompanied by a 12 percent reduction in pedestrian injuries.
At the start of the comparison period, City X lowered speed limits on most arterials and doubled traffic-enforcement patrols.
The bike-lane project cost the city nearly five million dollars to complete.
Nearby City Y, which has no protected bike lanes, saw no decline in collisions during the same months.
Surveys conducted after installation show that cyclists feel much safer using the new lanes.
Explanation
The argument assumes no other changes could explain the decline; A introduces a plausible alternative cause. The other choices either strengthen the claim or address issues (cost, perceptions) that do not bear on the causal link.
Which one of the following, if true, most seriously weakens the argument?
Young founders are more common in fast-moving industries than in heavily regulated ones.
Employee surveys indicate that staff value prior experience in top leadership.
The company's current CEO is nearing retirement age.
Across firms matched for industry and size, companies led by older CEOs produce more patents and patent citations than those led by younger CEOs.
A prominent young CEO recently led a revolutionary product launch in our sector.
Explanation
The conclusion generalizes from a correlation to a hiring rule. Evidence that, controlling for relevant factors, older-led firms generate more and higher-impact patents undermines the claim that youth inherently drives innovation; the other options are anecdotal or irrelevant.
Which one of the following, if true, most seriously weakens the argument?
The bakery plans to run blind taste tests next week.
The bakery's regular bread recipe was unchanged on the launch day.
The three comments came from members of a gluten-free club visiting together, and the new bread accounted for fewer than 10 percent of loaves sold that day.
In online reviews, several patrons praised the bakery's willingness to innovate.
The bakery used a new oven on the launch day.
Explanation
The argument hastily generalizes from a tiny, non-representative sample. Choice C shows the commenters were a biased group and that sales did not reflect broad preference, undermining the conclusion. The other options do not address representativeness.
Which one of the following, if true, most seriously weakens the argument?
Park attendance spikes on days when food trucks are present because those days coincide with city festivals; on festival days when food trucks were temporarily barred due to permitting issues, litter levels were just as high.
Most food trucks now use compostable containers.
Many residents say food trucks enliven the park atmosphere.
The city already prohibits food trucks from operating after 9 p.m.
Nearby restaurants have recently introduced lunch discounts to compete with food trucks.
Explanation
The argument assumes food trucks cause the litter rather than accompanying higher attendance. Choice B offers an alternative explanation and shows litter remains high even without trucks on comparable high-traffic days, undermining the causal claim. The other options are irrelevant to the cause of litter or merely about preferences and regulations.
Which one of the following, if true, casts the most doubt on the conclusion above?
Many mural unveilings attract local business sponsorships.
The city's mural grants are awarded only to neighborhoods that already have sustained low crime or have documented three-year declines before applications are accepted.
Some high-crime areas lack suitable wall space for large public murals.
Residents in mural-rich neighborhoods report strong community pride.
In two districts that added murals last year, graffiti complaints fell near the mural sites.
Explanation
If murals are preferentially sited in areas already low in crime or trending downward, the observed correlation does not show that murals cause crime reductions. The other options either support the proposal or raise issues that do not undercut the causal inference.
Which one of the following, if true, most seriously weakens the argument?
The museum's membership levels remained flat over the same month.
The city hosted a month-long cultural festival that drew record numbers of tourists to the area.
Historically, social media engagement correlates only weakly with actual museum attendance.
The museum's ticket prices did not change during the month after the exhibit opened.
Visitor surveys list the dinosaur exhibit as the most memorable attraction.
Explanation
A citywide festival could explain the attendance spike independently of the exhibit, undermining the causal claim. The other choices either support the exhibit's impact or are marginal/irrelevant.
Which one of the following, if true, most seriously weakens the argument?
Downtown office rents in Riverton increased over the period in question.
Riverton simultaneously enacted substantial temporary tax credits for employers who located downtown.
The comparison cities share Riverton's climate and population size.
Ridership on the rail line exceeded projections during those two years.
Several large employers publicly cited the new rail line as a factor in choosing downtown locations.
Explanation
Tax credits provide a plausible alternative cause of downtown job growth, undermining the claim that rail caused the increase. The other choices either support the transit explanation or are neutral background facts.
Which one of the following, if true, most seriously weakens the argument?
Other nonprofits saw slight donation increases during the same quarter.
The report received national media coverage and was widely shared on social media.
Staff morale was higher during the quarter following the report.
A single bequest from an estate accounted for more than half of the donation increase that quarter and was arranged months before the report.
The nonprofit's website experienced a brief outage the month before the report's release.
Explanation
The argument assumes the report caused the donation surge. Choice B identifies an alternative cause that explains most of the increase and predates the report, directly undercutting the causal inference. The other options are irrelevant or weaker.
Which one of the following, if true, most seriously weakens the argument?
The 30 percent gap in sick days persisted during a severe flu season.
The company can deploy the app company-wide at minimal cost.
The app includes reminders to drink water and take short walks.
Employees who opted in were eligible for attendance bonuses that depended on limiting sick days, whereas nonusers were not.
The vendor reports high user satisfaction rates at other companies.
Explanation
The argument assumes the app caused fewer sick days rather than differences between the groups. If opt-in employees had incentives to avoid taking sick days, selection effects—not the app—could explain the difference.
Which one of the following, if true, most seriously weakens the argument?
Language academies often publish dictionaries that codify patterns that already exist in everyday use.
Regulations frequently impose compliance costs that can constrain innovation.
Entrepreneurs frequently use metaphors from language when describing market behavior.
People can communicate effectively across dialects without any central planner.
In many historical cases, unregulated markets produced monopolies and systemic failures that reduced consumer choice, whereas language evolution has no mechanism allowing a single actor to restrict everyone's options.
Explanation
The argument relies on an analogy between markets and languages; B highlights a crucial disanalogy by noting harms unique to unregulated markets that lack a language parallel. The other options either support the analogy or are irrelevant.