LSAT Quiz: Weaken

What this quiz covers

This quiz focuses on Weaken, giving you a quick way to practice the rules, question types, and explanations that matter most for LSAT.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

Question 1

1. At the start of the comparison period, City X lowered speed limits on most arterials and doubled traffic-enforcement patrols. (correct answer)
2. Nearby City Y, which has no protected bike lanes, saw no decline in collisions during the same months.
3. Surveys conducted after installation show that cyclists feel much safer using the new lanes.
4. The bike-lane project cost the city nearly five million dollars to complete.
5. The decline in collisions was accompanied by a 12 percent reduction in pedestrian injuries.

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.

Question 2

1. The museum's ticket prices did not change during the month after the exhibit opened.
2. Visitor surveys list the dinosaur exhibit as the most memorable attraction.
3. The museum's membership levels remained flat over the same month.
4. The city hosted a month-long cultural festival that drew record numbers of tourists to the area. (correct answer)
5. Historically, social media engagement correlates only weakly with actual museum attendance.

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.

Question 3

1. Several large employers publicly cited the new rail line as a factor in choosing downtown locations.
2. Ridership on the rail line exceeded projections during those two years.
3. The comparison cities share Riverton's climate and population size.
4. Downtown office rents in Riverton increased over the period in question.
5. Riverton simultaneously enacted substantial temporary tax credits for employers who located downtown. (correct answer)

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.

Question 4

1. In nearby lakes where Zeta was released five years ago, native fish populations declined after Zeta consumed large quantities of fish eggs along with algae. (correct answer)
2. In additional laboratory trials conducted last year, Zeta reduced algae substantially faster whenever algal density in the tank started out at higher concentrations.
3. In brackish coastal waters and other saltwater environments, Zeta cannot survive for more than a few days after being introduced to the habitat.
4. In regional watersheds studied over the past decade, agricultural runoff levels are strongly correlated with the observed severity of seasonal algal blooms.
5. In the laboratory aquariums used for the original study, the fish tested were captive-bred specimens rather than individuals caught in the wild.

Explanation: The conclusion claims that releasing Zeta will curb algal blooms WITHOUT harming native fish. The choice reporting that fish populations declined in nearby lakes after Zeta ate fish eggs directly undercuts the 'no harm to fish' half of the conclusion, using real field evidence rather than lab results. That is the strongest doubt. The trial showing Zeta reduces algae even faster at higher densities strengthens, not weakens, the claim about controlling blooms. Zeta's inability to survive in saltwater is irrelevant, since the plan targets freshwater lakes. The correlation between agricultural runoff and bloom severity concerns a different cause of blooms and says nothing about whether Zeta will help or harm; if anything it leaves room for Zeta to still help. The fact that lab fish were captive-bred raises only a minor generalizability worry—it does not show that wild fish would actually be harmed. Only the fish-egg finding gives concrete evidence that the predicted outcome fails in the field, so it is the single best answer.

Question 5

1. In a randomized rollout across similar blocks last year, blocks assigned new lights saw no significant change in crime relative to unlit control blocks. (correct answer)
2. New LED streetlights installed in the pilot program consume far less electricity and cost less to maintain than the older sodium models they replace.
3. The police union, along with several neighborhood associations, has publicly endorsed the mayor's plan to expand streetlighting across the city.
4. Recent surveys show that most residents report feeling noticeably safer walking alone at night along streets that are brightly and consistently lit.
5. Certain crimes, such as online fraud and workplace embezzlement, tend to occur at similar rates regardless of how well any given street is lit.

Explanation: The argument treats a correlation between brighter streets and less crime as proof that lighting causes the drop. The strongest weakener attacks that causal leap directly: a randomized rollout in which lit blocks saw no crime change compared with unlit control blocks shows lighting itself doesn't reduce crime, so the observed correlation likely reflects some other factor. The electricity-and-maintenance choice compares cost and efficiency of bulbs, which is irrelevant to whether lighting reduces crime. The union-and-associations endorsement reports who supports the plan, but popularity says nothing about whether it will work. The survey about residents feeling safer measures perception, not actual crime rates, and could even support the mayor. The online-fraud choice notes that some crimes are unaffected by lighting, but the mayor's claim is about the nighttime street crimes the lighting targets, so it doesn't undermine that claim. Only the controlled experiment tests the causal claim itself, so it is the single best answer.

Question 6

1. Many of the interviewed CEOs also exercise vigorously early each morning, well before they open any book or newspaper.
2. Some of the profiled CEOs prefer listening to audiobooks or podcasts rather than reading printed material each morning.
3. People who begin reading early in the morning consistently report feeling sharper and more focused throughout the entire workday.
4. The magazine relied entirely on habits self-reported by the small set of high-profile CEOs it chose to profile.
5. A large longitudinal study finds no relationship between reading time of day and career advancement once education and industry are controlled. (correct answer)

Explanation: The columnist treats a shared habit among successful CEOs as a cause of their success. The winning answer directly tests that causal claim: a large study that controls for education and industry finds no link between when people read and how far they advance. If the correlation vanishes once relevant factors are held constant, the case for reading causing success collapses. The choice about CEOs also exercising early actually points to a rival cause, but it does not disprove that reading helps, so it weakens only weakly. The choice about some CEOs using audiobooks quibbles with the format of reading, not with whether the habit drives achievement. The choice about early readers feeling sharper reports a perceived benefit and thus supports, rather than undermines, the conclusion. The choice about self-reported habits from a small profiled group raises a data-quality worry, but unreliable reporting does not show the practice fails to help; it only questions how the columnist gathered examples. Only the longitudinal finding attacks the causal conclusion itself.

Question 7

1. The bakery's regular bread recipe was unchanged that launch day, and its longtime customers continued buying it at their usual rate throughout the morning.
2. In online reviews posted after the launch, several loyal patrons praised the bakery's general willingness to innovate and test out unfamiliar new recipes.
3. 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. (correct answer)
4. The bakery installed a new commercial oven that launch day, which produced a noticeably crisper crust on every loaf, including the standard regular bread.
5. The bakery plans to run carefully controlled blind taste tests next week to compare the gluten-free recipe against its established regular loaf.

Explanation: The argument leaps from three positive comments to the sweeping claim that most customers prefer the new bread. To weaken it, you want evidence that those three commenters were not representative and that broad preference never actually showed up. The correct choice does exactly this: the three writers were a gluten-free club visiting together (a self-selected, biased group), and the new bread was fewer than 10 percent of loaves sold, so the vast majority of purchasers chose the regular bread. That directly undercuts 'most customers prefer' the new loaf. The choice about the regular recipe being unchanged and selling at its usual rate is neutral-to-harmful for weakening—steady regular sales don't overturn the preference claim by themselves and were already implied by comparable totals. Praise for the bakery's willingness to innovate is off point; enthusiasm for experimentation says nothing about which bread most customers prefer. The new oven producing a crisper crust affects all loaves equally, so it doesn't explain away the taste comments or reveal an unrepresentative sample. Planned future blind taste tests provide no present evidence at all—they can't weaken a conclusion drawn today. Only the biased-sample-plus-tiny-share choice attacks representativeness, which is the argument's real vulnerability.

Question 8

1. Brand X is typically priced a few dollars cheaper per bottle than the competing name-brand oils this shop currently stocks.
2. The mechanic used the exact manufacturer-recommended viscosity for that sedan and followed every step on the shop's standard service checklist.
3. The engine failure occurred well within the mileage range that both the manufacturer and Brand X recommend between oil changes.
4. Brand X's national advertising campaigns emphasize superior protection and durability for high-performance and high-mileage engines alike.
5. An independent inspection found a preexisting head-gasket leak that allowed coolant into the oil, a common cause of engine seizure regardless of oil brand. (correct answer)

Explanation: The argument leaps from a single case to the conclusion that Brand X caused the failure. The head-gasket leak weakens this because it names a specific alternative cause—coolant entering the oil—that would seize the engine no matter which oil was used, breaking the assumed link between Brand X and the breakdown. The cheaper price of Brand X is irrelevant to why the engine failed. That the mechanic used correct viscosity and followed the checklist actually rules out one confound, if anything supporting the mechanic's suspicion rather than undermining it. That the failure happened within the recommended change interval does nothing to identify another cause; it merely times the event. The advertising claim about protecting high-performance engines describes marketing, not what actually happened to this car, so it cannot address whether the oil caused the seizure. Only the preexisting mechanical fault supplies a real competing explanation, so it is the one that most seriously weakens the argument.

Question 9

1. Solar chargers and backup power banks now make it far easier for hikers to keep their GPS devices running throughout multi-day trips.
2. Mountainous terrain, dense forests, and rapidly changing weather make natural cues unreliable for hikers, and emergency responders rely on GPS to locate lost hikers. (correct answer)
3. Many experienced hikers already supplement their GPS devices with paper maps and printed trail guides in case the electronics stop working.
4. The traditional celestial and dead-reckoning techniques once used by sailors are still taught in the certification courses that modern ship navigators complete.
5. Consumer GPS units have become significantly cheaper and more widely available over the past decade, putting them within reach of nearly all hikers.

Explanation: The argument reasons by analogy: because sailors navigated without digital aids, hikers should be able to abandon GPS and rely on natural cues. To weaken it, you need evidence that natural cues actually fail hikers or that GPS serves a purpose the analogy ignores. Pointing out that mountainous terrain, dense forests, and shifting weather make natural cues unreliable — and that rescuers depend on GPS to find lost hikers — directly attacks the assumption that reading sun and moss can safely replace GPS. That is the best answer. Noting that solar chargers make GPS easier to keep running says nothing about whether hikers could do without GPS; if anything it concerns keeping the device, not replacing it. That experienced hikers already carry paper maps shows only a habit of redundancy, not that natural cues are insufficient. That sailors' techniques are still taught in navigation courses tends to support, not undermine, the claim that such methods still work. That GPS units have gotten cheaper addresses cost and availability, which are irrelevant to whether natural cues are a safe substitute. Only one choice targets the analogy's core assumption about the reliability of natural cues.

Question 10

1. After a comparable ban in another city, taxi cruising and private drop-offs increased, and measured congestion worsened. (correct answer)
2. GPS data show rideshare drivers often double-park, blocking a lane for several minutes.
3. The ban is scheduled to be reevaluated in six months.
4. Rideshare cars account for nearly a quarter of peak-hour entries into the district.
5. The city plans to add new delivery loading zones next year.

Explanation: The council assumes removing rideshares will reduce congestion, ignoring substitution by taxis and private cars. Evidence from a similar policy that congestion worsened undercuts that causal assumption; the other choices either bolster the premise or are tangential.

Question 11

1. Humor scripts are generally cheaper and faster to produce than the dramatic scripts many insurance competitors currently favor in their national campaigns.
2. Several direct competitors plan to increase their overall advertising spending this year across both footwear and financial-services product lines.
3. The viral sneaker campaign ran during summer, a historically strong sales season for footwear among younger first-time buyers nationwide.
4. Industry studies show humorous insurance ads are rated less credible and generate lower purchase rates than straightforward informational ads among target-age consumers. (correct answer)
5. Brand awareness for our sneaker line is already high among teenagers, though considerably lower among the older adults who typically purchase policies.

Explanation: The conclusion rests on an analogy: because humor boosted sneaker sales, a lighthearted tone will boost life insurance sign-ups too. To weaken it, you need evidence that humor does NOT transfer to the insurance category. The claim that humorous insurance ads are rated less credible and produce lower purchase rates than informational ads directly attacks that analogy for the exact product and audience in question. The cost claim about cheaper humor scripts speaks to production budget, not to whether humor will actually persuade insurance buyers. The competitors' rising ad spending is about market conditions, not about whether humor works for this product. The summer-season point offers an alternative explanation for the sneaker success, which slightly undercuts the analogy's strength but says nothing about insurance effectiveness, so it is weaker than the direct evidence. The high teen brand awareness point actually hints that the sneaker audience differs from insurance buyers, but it addresses recognition, not tone, and does not show humor fails for insurance. Only one choice provides category-specific evidence that the humorous approach underperforms, so it casts the most doubt.

Question 12

1. In a survey conducted last spring, many Brookdale residents said they generally prefer natural herbal remedies over conventional pharmaceutical medications.
2. Laboratory analyses of ElderLeaf identified several plant-derived compounds that measurably reduced viral replication when tested on infected cells in a petri dish.
3. In a randomized, double-blind clinical trial in a neighboring city, participants taking ElderLeaf had the same flu incidence as those taking a placebo. (correct answer)
4. Some Brookdale residents who took ElderLeaf regularly this winter reported experiencing mild stomach discomfort and occasional nausea after their daily dose.
5. Local clinics diagnosing influenza this winter applied the same standardized diagnostic criteria that they had used in each of several previous years.

Explanation: The argument leaps from a correlation—daily ElderLeaf users had less flu—to a causal claim that ElderLeaf prevents flu. A randomized, double-blind trial comparing ElderLeaf against placebo controls for the self-selection behind that correlation; finding no difference in flu incidence directly undercuts the causal claim, so it is the strongest weakener. The survey about residents preferring natural remedies is off-topic; it says nothing about whether ElderLeaf works. The petri-dish finding of reduced viral replication, if anything, mildly supports the claim rather than weakening it, and in-dish activity does not establish real-world prevention. The report of stomach discomfort concerns a side effect, not effectiveness against flu. The consistency of diagnostic criteria across years merely rules out one measurement artifact, which if anything makes the observed correlation more trustworthy—the opposite of weakening. Only the placebo-controlled trial breaks the causal inference the argument depends on.

Question 13

1. Frequent users of the app reported larger sleep gains than infrequent users.
2. The app's meditations were designed with input from licensed clinicians.
3. The survey did not ask respondents about the quality of their mattresses.
4. Many respondents said they planned to continue using the app for several months.
5. In a randomized controlled trial, people assigned to this app improved no more than those assigned to a control app that only played white noise. (correct answer)

Explanation: The claim is based on a self-selected survey; E provides experimental evidence that the app performs no better than a control, undermining a causal claim. The other choices either support the app or raise minor, non-dispositive concerns.

Question 14

1. Reliora users in the study were more likely to believe in natural remedies than nonusers.
2. Reliora is inexpensive and widely available at local pharmacies.
3. Some participants who did not take Reliora tried other over-the-counter remedies.
4. Reliora users in the study were substantially more likely than nonusers to adopt a physician-recommended sleep and hydration regimen known to reduce headaches. (correct answer)
5. Headache frequency tends to fluctuate seasonally in the region where the study was conducted.

Explanation: The argument assumes Reliora caused the reduction. If users also adopted a regimen independently known to cut headaches, that provides an alternative explanation; the other choices do not directly account for the observed difference.

Question 15

1. Some evening diners at the surveyed locations say they prefer lighter, smaller dishes when they go out to eat on weekend nights.
2. The chain rarely promotes its weekday lunch specials during weekend dinner service, though staff mention them to interested tables when asked.
3. The Friday and Saturday sample deliberately included a balanced mix of both urban downtown locations and quieter suburban strip-mall branches.
4. Weekday lunch patrons are mostly nearby office workers; a separate survey of them shows strong demand for the lunch specials. (correct answer)
5. Eliminating the weekday lunch menu companywide would reduce kitchen complexity and free up prep space during busy dinner hours.

Explanation: The argument surveys only weekend evening diners, then concludes the weekday lunch menu is unpopular and should be dropped. That reasoning holds only if evening diners represent the people who would actually order lunch. The correct answer breaks that link: weekday lunch patrons are a different group — nearby office workers — and a survey of them shows strong demand. This makes the original sample unrepresentative and directly undermines the 'unpopular' conclusion. The claim that some evening diners prefer lighter weekend dishes is beside the point; it says nothing about weekday lunch demand and doesn't challenge the sample's relevance. That the chain rarely promotes the specials at dinner might explain low awareness among evening diners, but it doesn't establish that lunch patrons want the menu, so it can't rescue it as strongly. The urban-suburban mix describes geographic variety but ignores the real flaw — surveying dinner guests rather than lunch guests. Reduced kitchen complexity is a reason to eliminate the menu for operational convenience, not evidence about popularity, so it supports the plan rather than weakening the argument. Only the office-worker survey shows the wrong population was measured.

Question 16

1. Some competing firms migrate to cloud services primarily to reduce their spending on hardware, staffing, and physical facility maintenance over time.
2. Independent privacy watchdogs certify certain cloud providers as exceeding most in-house systems in privacy protections when configured with end-to-end encryption and zero-trust access. (correct answer)
3. A competitor relying on a large public cloud platform recently suffered a serious data breach that investigators traced directly to that outside provider.
4. Our firm recently completed a rigorous third-party audit confirming that its in-house access logs are reviewed thoroughly by security staff every single day.
5. Regulators impose substantial fines for mishandling personal client data regardless of whether a company relies on cloud platforms or on-premises systems.

Explanation: The argument concludes that avoiding cloud services proves the firm has superior privacy, resting on the premise that shared cloud environments are inherently less private. The correct answer directly attacks that premise: if independent watchdogs certify that properly configured cloud providers can exceed in-house systems in privacy, then keeping data on physically controlled servers does not guarantee better privacy, and the conclusion collapses. The claim about firms migrating to cut hardware and staffing costs is off-topic—it explains why some choose the cloud but says nothing about relative privacy. The competitor's traced breach actually supports the firm's position by suggesting clouds are risky, so it strengthens rather than weakens. The firm's own audit showing daily log review also strengthens the case for its in-house approach. The point about regulators fining companies regardless of platform is irrelevant to which system offers greater privacy; equal penalties don't address the comparative claim. Only the certification finding undermines the reasoning connecting cloud avoidance to superior confidentiality.

Question 17

1. Many museum patrons also attend concerts at the same performing arts complex.
2. The museum's last admission increase was followed by a noticeable drop in attendance among nonmembers despite expanded programming. (correct answer)
3. Concertgoers typically value the uniqueness of live performances, whereas museum exhibits change monthly.
4. The museum offers one free-admission day each month.
5. A nearby city's museum charges more than ours and often has lines out the door.

Explanation: The argument relies on an analogy to concerts to claim inelastic demand for museum tickets. Direct evidence that a past price increase reduced attendance undermines that assumption; the other options either support the analogy or are irrelevant.

Question 18

1. Some commuters say they resent the fee and intend to keep driving downtown.
2. During the first month, two major subway lines serving downtown were closed for repairs, a situation scheduled to end next month. (correct answer)
3. The city plans to dedicate fee revenue to building new bus-only lanes over the next two years.
4. Surveys show many downtown workers drive because their employers subsidize parking.
5. Congestion fees have generated controversy in several other cities that adopted them.

Explanation: If unusual transit disruptions masked the fee's effect during the first month, the lack of an immediate reduction in traffic provides little evidence about the fee's long-term impact. The other choices either support the pessimistic view or are irrelevant policy details.

Question 19

1. Most residents reported switching to reusable shopping bags for their groceries in the months immediately following the town's ban.
2. Several neighboring towns are currently considering similar plastic bag bans, but none of them has yet formally enacted such a measure.
3. During the same period, a state program removed large quantities of discarded fishing gear from coastal waters near the town. (correct answer)
4. Plastic bag manufacturers have filed a lawsuit challenging the town's ban, arguing that the ordinance exceeds the local government's authority.
5. The town increased fines for littering in its public parks and playgrounds during the year before the bag ban took effect.

Explanation: The argument concludes that the bag ban caused the drop in ocean plastic. Any information suggesting another cause for that drop weakens it. The state program that removed large quantities of discarded fishing gear from the same coastal waters during the same period offers exactly such an alternative cause: the decline may reflect the cleanup, not the ban. This directly undercuts the causal claim. Residents switching to reusable bags actually supports the idea that the ban changed behavior, so it strengthens rather than weakens the argument. Neighboring towns merely considering bans says nothing about whether this town's ban worked. A manufacturers' lawsuit challenges the ban's legality, not whether it reduced pollution. Higher fines for littering in parks and playgrounds target land litter before the ban and do not explain a decrease specifically in coastal water plastic during the survey period. Only the competing cleanup provides a genuine rival explanation for the measured change.

Question 20

1. Several competing publications have recently increased the proportion of long-form content on their own sites, and their overall readership numbers have climbed steadily as a result.
2. The magazine's staff writers consistently report far greater job satisfaction when producing longer, more researched pieces than when writing routine short news briefs.
3. The magazine's editors already plan a comprehensive site redesign intended to improve overall readability and navigation on mobile devices within the coming year.
4. The online poll was restricted to readers who spent more than five minutes on the site, whereas most visitors bounce after reading only brief items. (correct answer)
5. A small but vocal group of longtime print subscribers recently emailed the editor directly to request more in-depth, longer feature articles across every section.

Explanation: The conclusion assumes the poll's respondents represent the magazine's whole audience. If the poll counted only readers who stayed more than five minutes, while most visitors leave after skimming brief items, then the majority favoring long-form articles is an unrepresentative slice—the very readers most likely to prefer length. That undercuts the leap from 'polled readers prefer long-form' to 'the audience prefers long-form,' so it casts the most doubt. What competing publications do with their own long-form content and readership says nothing about what this magazine's audience wants. Staff writers' greater satisfaction concerns the people producing articles, not the audience the conclusion is about. A planned redesign to improve mobile readability addresses format and navigation, not article length, and does not bear on the poll's reliability. A small group of print subscribers emailing for longer features is weak, self-selected evidence that, if anything, mildly supports lengthening—it does not weaken the conclusion. Only the sampling problem in the poll challenges the reasoning.