- A health blogger argues: In a small group of friends, those who started drinking a glass of water before each meal reported losing more weight over two months than those who did not. Drinking water can reduce hunger, so it makes sense that they ate less. Since eating less leads to weight loss, the water-before-meals habit must be an effective weight-loss method. Therefore, most people who adopt this habit will lose weight, even without making any other changes.
Which one of the following, if true, most seriously weakens the argument?
Answer: Several people in the group who drank water before meals also began tracking calories and increasing their weekly exercise.
The health blogger concludes that drinking water before meals causes weight loss based on observations from a small group of friends. The argument assumes the water habit was responsible for the weight loss difference. Answer A devastates this conclusion by revealing that the water-drinking group also made other significant lifestyle changes—tracking calories and increasing exercise—which are well-established weight loss methods. This shows that the weight loss could be entirely due to these other factors rather than the water consumption. Answer D might seem relevant by suggesting pre-existing differences between groups, but preference for sugary beverages doesn't explain the weight loss as directly as actual behavior changes. When multiple factors change simultaneously, you cannot attribute the outcome to just one factor without controlling for the others.
- A professor claims that allowing students to use laptops in class reduces learning. She points out that in her course last term, students who took notes on paper scored higher on the final exam than students who used laptops. She also notes that laptops can distract students with messaging and websites. Therefore, she concludes that banning laptops in all courses at the university will improve overall student performance. Which one of the following, if true, most seriously weakens the argument?
Answer: Students who used paper notes in the professor's course were more likely to have taken advanced courses in the subject beforehand.
The professor concludes that a university-wide laptop ban will improve performance, based on paper note-takers outscoring laptop users in one course. This assumes the note-taking method caused the score gap. The answer noting that paper note-takers were more likely to have taken advanced courses in the subject exposes a selection-bias flaw: those students may have scored higher because of stronger background preparation, not because paper is superior. That reversal is exactly what weakens the argument. The choice about using laptops for digital readings shows one legitimate laptop use, but it does not challenge the claim that laptops hurt performance overall. The choice about students preferring handwriting reports a preference, not evidence that handwriting actually raises exam scores. The choice about limited electrical outlets addresses a practical constraint on charging, not whether banning laptops improves learning. The choice about professors discouraging social media concerns existing classroom norms and, if anything, mildly supports the distraction claim rather than undermining the conclusion. Only the selection-bias answer offers an alternative explanation for the observed score difference, so it is the strongest weakener.
- Which one of the following, if true, most seriously weakens the argument?
Answer: During those six months, a large distribution center and a call center opened in Metrovale, together hiring several thousand entry-level workers.
The argument claims the wage increase caused unemployment to fall. To weaken a causal claim, look for an alternative cause of the observed drop. The correct answer supplies exactly that: two big new facilities hiring thousands of entry-level workers would lower unemployment regardless of the wage change, breaking the assumed link. The choice about neighboring cities that kept wages flat and saw steady unemployment actually points the other way—if anything, it mildly supports the argument by contrast, so it cannot weaken it. The choice about businesses raising prices and trimming a few hours describes minor side effects but leaves the unemployment-drop causal story intact; slightly fewer hours is not the same as higher unemployment. The polling choice concerns public opinion, which is irrelevant to whether the wage increase actually caused the change in unemployment. The choice about economists disagreeing is too general: expert disagreement in the abstract does not address what happened in Metrovale specifically. Only the new-employers choice offers a concrete rival explanation for this particular decline.
- A school district piloted a new math app in two middle schools and found that, by the end of the semester, students using the app scored higher on a standardized math test than students in other district schools. The two pilot schools also had smaller average class sizes and recently hired additional math tutors. Because the app was the only new instructional tool introduced districtwide, the superintendent concludes that adopting the app in all schools will raise math scores across the district. Which one of the following, if true, most seriously weakens the argument?
Answer: The pilot schools' students had higher math scores than other district students even before the app was introduced.
The argument concludes that adopting the math app districtwide will raise scores, based on higher test performance in two pilot schools that used the app. The reasoning assumes the app caused the improved scores. However, choice B reveals a crucial pre-existing difference: the pilot schools' students already had higher math scores before the app was introduced. This means the observed difference could be due to these schools having stronger students to begin with, not the app's effectiveness. The argument commits the classic error of ignoring baseline differences between test and control groups. Choice E is tempting because it suggests the test was biased toward app users, but this would actually support the app's effectiveness rather than weaken it. Effective weakening answers in comparative studies expose pre-existing differences that could account for observed performance gaps.
- A financial advisor says that people who automatically transfer part of each paycheck into savings accounts tend to accumulate more savings than people who do not. She reasons that automation prevents people from spending money they might otherwise save. Therefore, she concludes that encouraging all clients to set up automatic transfers will ensure that most of them build substantial emergency funds within a year. Which one of the following, if true, casts the most doubt on the conclusion above?
Answer: Clients who set up automatic transfers often already have higher incomes and fewer monthly expenses than other clients.
The argument concludes that encouraging automatic transfers will ensure most clients build substantial emergency funds within a year, based on observing that automatic transfer users accumulate more savings. The reasoning assumes automation prevents spending and creates saving discipline. However, choice A reveals a selection bias: clients who set up automatic transfers often already have higher incomes and fewer monthly expenses. This means they have greater capacity to save regardless of the transfer method. The correlation exists because financially stable clients choose automated tools, not because automation creates saving ability. Choice E is tempting as it identifies a barrier to automatic transfers, but irregular pay schedules don't directly challenge whether automation helps when feasible. Arguments about financial behavior must account for underlying economic differences between groups that could drive both tool adoption and outcomes.
- Which one of the following, if true, most seriously weakens the argument?
Answer: Unlike bees, employees in companies often have divergent incentives and specialized knowledge requiring explicit coordination.
The argument relies on an analogy that assumes relevant similarity between bee colonies and firms. Pointing out crucial differences in incentives and coordination needs directly undercuts the analogy; the other options are irrelevant or only suggest isolated exceptions.
- A city council member argues that installing brighter streetlights in one neighborhood reduced nighttime crime there. She notes that in the six months after the new lights were installed, reported nighttime thefts in that neighborhood fell by 25% compared with the previous six months. She also points out that the police department did not add officers assigned to that neighborhood during that time. Therefore, she concludes, brighter streetlights are an effective crime-reduction tool and the city should install them in every neighborhood to reduce nighttime thefts citywide. Which one of the following, if true, casts the most doubt on the conclusion above?
Answer: During the same six months, a private security company began patrolling several apartment complexes in the neighborhood at night.
The council member concludes that brighter streetlights caused the 25% reduction in nighttime thefts, assuming the lights were the only relevant change in the neighborhood. Answer (A) severely weakens this by introducing a competing explanation: a private security company began patrolling apartment complexes at night during the same period. This alternative cause could easily account for the crime reduction, making it impossible to attribute the improvement solely to the streetlights. Answer (E) might seem relevant because it mentions daytime thefts also decreasing, but this actually suggests a broader crime reduction trend rather than undermining the streetlight explanation. The strongest weakening answers in causal arguments introduce plausible alternative causes that occurred simultaneously with the proposed cause.
- Which one of the following, if true, casts the most doubt on the conclusion above?
Answer: Subscribers to Luxe Travel are predominantly affluent beach-resort enthusiasts and are not representative of typical tourists.
The conclusion generalizes from a clearly biased sample to all tourists. Showing that the magazine's readers are unrepresentative directly undermines that generalization; the other options either support the trend or are irrelevant.
- Which one of the following, if true, casts the most doubt on the conclusion above?
Answer: When average weekly exercise and sleep are held constant, the difference in reported energy between ginseng users and nonusers disappears.
The argument treats a correlation between ginseng use and reported energy as proof that ginseng causes energy. The claim that holding exercise and sleep constant makes the energy difference vanish is the strongest attack: it shows the difference tracks lifestyle, not ginseng, exposing a confounding variable the survey never measured. Reporting that ginseng users also drink more water names another correlated habit but never shows it explains away the energy gap, so it doesn't undermine the causal claim. A randomized, placebo-controlled trial finding higher energy in ginseng users actually strengthens the conclusion by supplying controlled causal evidence. Verifying unique IP addresses only guards against duplicate responses, addressing a data-integrity concern rather than the leap from correlation to cause. Drawing respondents from all 50 states and territories speaks to geographic breadth and generalizability, not to whether ginseng itself produces the energy difference. Only the exercise-and-sleep result targets the actual gap in the reasoning.
- A university surveyed 30 students who attended a new weekend workshop on study skills. Most of them said they felt more confident about managing their time afterward, and several reported higher quiz scores in the following week. Since confidence and early score gains indicate improved study habits, the workshop clearly makes students perform better academically. Therefore, the university should require all students to take the workshop because it will raise overall grades across campus.
Which one of the following, if true, most weakens the argument?
Answer: Many students who enrolled in the workshop were already motivated and had sought out other academic support services.
The argument concludes that the study skills workshop makes students perform better academically and should be required for all students, based on 30 workshop attendees reporting higher confidence and some showing improved quiz scores. The argument assumes the workshop itself caused these improvements. However, choice A reveals a critical selection bias: many students who enrolled were already motivated and had sought out other academic support services. This means the workshop participants were not representative of the general student population—they were already high-achievers who would likely improve regardless of the workshop. Choice C about placebo effects is tempting, but it's speculative compared to the concrete bias issue. Strong weakening answers often expose flawed sampling or selection effects that make the evidence unrepresentative of the broader conclusion.
- After the city installed brighter LED streetlights on Maple Avenue, reported car break-ins on that street fell by 30% over the next three months. During the same period, the police department also increased nighttime patrols downtown, but not on Maple Avenue. Residents on Maple Avenue say they now feel more comfortable parking on the street and are more likely to notice suspicious behavior. Since the only major change on Maple Avenue itself was the new lighting, the brighter streetlights must have been the main reason break-ins decreased there. Which one of the following, if true, most seriously weakens the argument?
Answer: Police reports show that car break-ins typically decline citywide during the winter months, regardless of lighting changes.
The argument concludes that brighter streetlights caused the 30% decrease in car break-ins on Maple Avenue, based on the timing correlation and the claim that lighting was the only major change. However, this reasoning assumes that no other factors could explain the decline. Choice D directly undermines this assumption by revealing that car break-ins naturally decline citywide during winter months regardless of lighting changes—providing an alternative explanation for the observed decrease. This suggests the reduction might be due to seasonal patterns rather than the new lights. Choice A is tempting because it mentions another change (security cameras), but this would actually strengthen the argument by showing additional crime prevention measures were implemented. The strongest weakening answers in causal arguments identify alternative explanations that could account for the observed effect without invoking the proposed cause.
- Which one of the following, if true, most seriously weakens the argument?
Answer: Independent toxicology research shows the compound bioaccumulates and tumor rates in rats spike after 18 months of exposure.
The company concludes the compound is safe for long-term human use, but its only evidence is a six-month rat study. The correct answer shows that harm can emerge later: the compound bioaccumulates and rat tumor rates spike after 18 months. This directly undermines the leap from a short study to a long-term safety claim, so it most seriously weakens the argument. The choice about the rat strain being standard for cancer testing actually supports the study's credibility, so it strengthens rather than weakens. The claim that the compound breaks down quickly in sunlight might reduce environmental exposure, but it says nothing about the carcinogenic risk of long-term use and does not challenge the reasoning. Farmers' preference for low-toxicity labels concerns purchasing behavior, not whether the compound is actually carcinogenic, so it is irrelevant to the conclusion. The requirement of testing for aquatic species addresses a different regulatory category and does not bear on human carcinogenic risk. Only the first choice attacks the crucial gap between short-term data and a long-term conclusion.
- A museum director notes that attendance rose sharply during the months when the museum offered free guided tours every afternoon. Since the tours highlight key works and help visitors appreciate the exhibits, the director concludes that offering free tours is what caused the attendance increase and that continuing the tours will keep attendance high. Which one of the following, if true, most seriously weakens the argument?
Answer: During the same months, the museum hosted a widely advertised traveling exhibit that was not available at any nearby museum.
The director assumes the free tours caused the attendance spike simply because attendance rose during the same months the tours ran. To weaken this, you need a rival explanation for the increase. The correct answer supplies one: a widely advertised traveling exhibit, available nowhere nearby, ran during those exact months. That unique draw could fully account for the surge, meaning the tours may deserve little or no credit—so continuing them might not keep attendance high. The choice about some visitors preferring to explore on their own doesn't address why overall attendance rose; a preference of some people is consistent with tours still driving the increase. The choice about well-trained guides supports the value of tours if anything, so it strengthens rather than weakens. The choice about rising gift-shop revenue merely restates that attendance was higher without explaining the cause—it's a symptom, not an alternative cause. The choice about surveyed visitors saying they came for the tours is tempting, but a few self-reports don't show the tours drove the overall increase, and it actually points toward the tours mattering. Only the traveling-exhibit choice offers a competing cause that undermines the director's conclusion.
- Which one of the following, if true, casts the most doubt on the conclusion above?
Answer: The meter contract requires ongoing software subscriptions and debt service that exceed the projected savings from reduced pumping and treatment.
The officials conclude that installing meters will produce net budget savings next year, assuming reduced water use automatically means the city spends less overall. The correct answer breaks that assumption by naming a cost the argument ignored: ongoing subscription fees and debt service that are larger than the pumping and treatment savings, so the budget would not shrink. The claim about neighboring cities' sustained reductions actually supports the officials, since it confirms usage will fall. The point about meters detecting home leaks describes a customer benefit and, if anything, reinforces conservation rather than raising a budget problem. Residents supporting conservation for environmental reasons speaks to public attitudes, not to whether the city saves money. The plant idling pumps to cut electricity costs likewise strengthens the savings case instead of doubting it. Only one choice introduces new costs that erase the projected relief, so it alone weakens the conclusion.
- A neighborhood association planted trees along a busy road, and residents soon reported less noise in their homes. A sound meter placed near the road also showed slightly lower average decibel readings than before. Since trees act as barriers that absorb and deflect sound, the tree planting reduced road noise. Therefore, planting trees along all major roads in the city will substantially solve the city's traffic-noise problem.
Which one of the following, if true, most weakens the argument?
Answer: During the same period, the city repaved that road with a quieter asphalt designed to reduce tire noise.
The argument concludes that tree planting reduced road noise and that planting trees along all major roads will substantially solve the city's traffic-noise problem, based on resident reports and lower sound meter readings after trees were planted. The argument assumes the trees caused the noise reduction. However, choice A reveals that during the same period, the city repaved that road with quieter asphalt designed specifically to reduce tire noise. Road surface changes would have a direct and immediate impact on traffic noise levels, providing a compelling alternative explanation for both the residents' perceptions and the measured decibel reductions. Choice E about vegetation reducing noise is tempting because it supports the general principle, but it strengthens the argument rather than weakening it. Strong weakening answers identify concurrent interventions that target the same problem through different mechanisms.
- A city council member argues that installing more streetlights in Riverside Park will reduce crime there. Last year, the city added streetlights to two smaller parks, and police reports show that nighttime thefts in those parks dropped noticeably afterward. In Riverside Park, most reported thefts also occur at night near poorly lit paths. So, if the city adds streetlights throughout Riverside Park, crime in that park will decline, and residents will feel safer using it after dark.
Which one of the following, if true, most weakens the argument?
Answer: Police increased nighttime patrols in the two smaller parks at the same time the new streetlights were installed.
The argument's conclusion is that adding streetlights to Riverside Park will reduce crime and improve safety, assuming the lights caused the theft drop in smaller parks without considering other concurrent changes. This hinges on a flawed causal assumption, ignoring possible confounders in the evidence from the smaller parks. Choice E undermines this by revealing increased police patrols happened simultaneously, offering an alternative reason for the crime reduction that isn't transferable to Riverside. A common trap like C posits a temporary thief exodus, but this is a speculative possibility without evidence, failing to directly weaken the lighting's attributed impact. The key insight for weaken questions is to target answers that introduce specific alternative causes, ensuring they disrupt the argument's central reasoning rather than peripheral details.
- A local newspaper reports that neighborhoods with more community gardens tend to have lower rates of littering. The paper adds that gardens bring neighbors together and give them a sense of pride in their streets. Therefore, the paper concludes, building additional community gardens in any neighborhood will reduce littering there. Which one of the following, if true, casts the most doubt on the conclusion above?
Answer: Neighborhoods that successfully create community gardens usually already have active neighborhood associations that discourage littering.
The argument concludes that building community gardens in any neighborhood will reduce littering, based on the correlation between gardens and lower litter rates. The reasoning assumes gardens cause the reduction in littering. However, choice C reveals a selection bias: neighborhoods that successfully create gardens typically already have active associations that discourage littering. This suggests the low litter rates exist before the gardens are built, not because of them. Gardens may simply be more likely to appear in neighborhoods that are already well-organized and clean. The argument mistakes correlation for causation by ignoring this reverse relationship. Choice A is tempting because it mentions additional cleanup activities, but this would support rather than undermine the conclusion about community engagement. When arguments claim one factor causes another based on correlation, look for evidence that the supposed effect actually precedes the supposed cause.
- Which one of the following, if true, most seriously weakens the argument?
Answer: Remote employees also receive monthly stipends and flexible hours unavailable to in-office staff; in a similar survey at a sister company where all employees had these benefits regardless of location, satisfaction did not differ by location.
The argument assumes that working remotely itself causes higher satisfaction, so expanding remote roles will raise it. The keyed choice undercuts this by revealing a confounder: remote staff also enjoyed extra benefits, and at a sister company where everyone received those benefits regardless of location, satisfaction did not differ by location. That points to the benefits, not the location, as the real driver of the gap. The choice about in-office employees preferring face-to-face work describes personal preferences but gives no reason satisfaction wouldn't rise if remote roles expanded—it may even fit the conclusion. The commute-time choice notes an unasked question and adds a detail that, if anything, supports remote work being more satisfying, so it fails to weaken the causal claim. The software-tools choice names a possible perk of working remotely but never shows location itself is irrelevant to satisfaction; it too could support the conclusion. The industry-trend choice about other companies shifting toward remote work is irrelevant to whether location causes this company's satisfaction difference. Only the sister-company evidence supplies a genuine alternative explanation and shows the difference disappears once benefits are held constant.
- Which one of the following, if true, most seriously weakens the argument?
Answer: 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.
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.
- Which one of the following, if true, most seriously weakens the argument?
Answer: Mountainous terrain, dense forests, and rapidly changing weather make natural cues unreliable for hikers, and emergency responders rely on GPS to locate lost hikers.
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.
