- A community college offered a free tutoring program for students in introductory chemistry. Among students who attended at least four sessions, the course pass rate was 85%, compared to 65% for students who did not attend. Since the same instructor taught all sections, the program coordinator concludes that tutoring caused the higher pass rate. Therefore, if the college expands the tutoring program to all difficult introductory courses, overall graduation rates will rise substantially, because more students will pass their required classes on the first try.
Which one of the following, if true, most strengthens the argument?
Answer: Students who attended at least four tutoring sessions were not, on average, better prepared in chemistry at the start of the term than those who did not attend.
The coordinator claims tutoring caused the higher pass rate, then predicts wider graduation gains. The biggest gap is selection bias: students chose to attend, so they might already have been stronger or more motivated in chemistry, meaning their higher pass rate reflects who they were, not the tutoring. Confirming that attendees were not, on average, better prepared at the start of the term rules out that alternative explanation, so the pass-rate gap is more plausibly caused by tutoring itself—exactly what strengthens a causal argument.
The option about a quiet room stocked with whiteboards and practice problems describes the setting but gives no reason to think tutoring, rather than pre-existing ability, produced the results. Scheduling conflicts among non-attendees explain why some students missed sessions but say nothing about whether attendees and non-attendees started out equally prepared, so the causal doubt remains. Weekly graded homework applied to everyone in the course, so it cannot explain why attendees passed at higher rates. That chemistry is harder than other sciences bears on whether the program is needed, not on whether tutoring actually caused the observed improvement. Only the preparation comparison closes the selection-bias gap.
- Which one of the following, if true, most strengthens the argument?
Answer: Fuel-price data and meteorological records show that gas prices were stable, weather typical, and no citywide events occurred that would boost transit use during those months.
The officials argue that the cheaper fare caused the ridership jump, but skeptics list rival explanations: gas prices, weather, and special events. The correct choice directly closes off exactly those rival causes—confirming gas prices were stable, weather was typical, and no citywide events occurred—so the fare change is left as the best remaining explanation. The strike choice actually weakens the argument: it offers a competing reason ridership looks higher, since last year's baseline was artificially low. The social-media choice is tangential; more followers or online reach doesn't establish that the fare cut, rather than anything else, drove ridership. The reliability-survey choice reports rider preferences, not any change that occurred during the period, so it cannot explain a rise tied to the fare cut—and it even hints price matters less. The low-income choice explains who benefited but not whether the fare cut, versus gas prices, weather, or events, caused the overall increase. Only the choice ruling out the named alternatives strengthens the causal conclusion.
- Which one of the following, if true, provides the most support for the conclusion above?
Answer: Testing shows equal rates of viral exposure in owls from logged and unlogged areas, but nesting success drops sharply within 1 km of new clear-cuts.
The conclusion is that logging, not disease, drives the owl decline. The best support pairs two facts: viral exposure is equal in logged and unlogged areas (undercutting the disease explanation), while nesting success falls sharply close to new clear-cuts (tying the decline directly to logging). Together these make logging the more likely cause.
The replanting-requirement fact tells us nothing about why owls are currently declining; a legal duty to replant does not link logging to the observed drop. The higher-rainfall fact actually introduces a rival cause—an environmental difference between reserves and logged tracts—so it weakens rather than strengthens the argument. The rise in predator populations likewise offers an alternative explanation for the decline that has nothing to do with logging. The camera-trap failures point to a measurement problem in the surveys but do not connect logging to the owl decline, and could even cast doubt on the data. Only the exposure-and-nesting evidence both rules out disease and ties the loss to logging, so it is the single best answer.
- A landlord argues that installing better insulation reduced tenants' heating costs. She notes that after insulation was added to an older apartment building, tenants' average winter heating bills were lower than the previous winter's bills. She also reports that tenants complained less about drafts and that the building's heating system ran less often, according to maintenance logs. Therefore, she concludes that the insulation caused the cost savings and that insulating her other buildings will reliably reduce tenants' heating costs as well. Since the bills fell after the installation and drafts decreased, she treats insulation as the main cause.
Which one of the following, if true, most strengthens the argument?
Answer: Tenants in similar nearby buildings without new insulation did not see comparable reductions in heating bills that winter.
The landlord argues that installing better insulation reduced tenants' heating costs, noting lower bills and fewer complaints about drafts. The argument's main weakness is not ruling out other factors that could explain lower heating bills. Answer choice C strengthens the argument by showing that tenants in similar nearby buildings without new insulation didn't see comparable bill reductions—providing a control group that isolates insulation as the causal factor. Choice A is tempting because it mentions a milder winter, but this would actually weaken the argument by providing an alternative explanation. When strengthening arguments about building improvements, use comparative data from similar properties to control for external factors like weather.
- Which one of the following, if true, most strengthens the argument?
Answer: In neighboring states where kiosk prices fell equally but minimum wage did not rise, adoption rates remained flat, while in State X adoption jumped immediately after the wage hike.
The argument claims the wage hike, not falling kiosk prices, drove State X's sudden adoption. The winning choice supplies a controlled comparison: neighboring states saw prices fall equally, yet with no wage rise their adoption stayed flat — while State X's adoption spiked right after its wage rose. Isolating the wage as the only differing factor directly supports the causal claim and rules out the price explanation. The advertising choice introduces a rival cause — a marketing push — which would compete with, not reinforce, the wage explanation. The restaurant-closures choice reports a possible effect of the wage hike but says nothing about why kiosks were adopted, so it is irrelevant to the causal question. The customer-preference choice, if anything, makes the rapid rollout more surprising and never links adoption to wages. The food-safety choice adds a second simultaneous change, creating an alternative explanation for the timing rather than strengthening the wage cause. Only the cross-state comparison pins the surge on the wage increase.
- Which one of the following, if true, provides the most support for the conclusion above?
Answer: In a double-blind randomized study of similar patients, those given Willowbark improved significantly more than those given a placebo.
The conclusion is that Willowbark itself reduces headaches, but the critic points out that expectation, other habit changes, or continued over-the-counter remedies could explain the 60 percent result. The double-blind randomized placebo-controlled finding directly rules out those alternatives: patients who couldn't know what they took still improved more on Willowbark than on placebo, so the effect isn't just expectancy or habit change. That's why it best supports the conclusion. The claim that many participants had tried other supplements without success tells us nothing about whether Willowbark caused this improvement. That Willowbark comes from a bark used in folk medicine is irrelevant background; long use doesn't establish effectiveness. Reports of mild nausea and dizziness concern side effects, not whether headaches actually decreased. And noting that hydration and sleep went untracked, if anything, highlights an uncontrolled alternative explanation rather than strengthening the causal claim.
- Which one of the following, if true, provides the most support for the conclusion above?
Answer: In a neighboring district that expanded tutoring and attendance efforts but did not change cafeteria offerings, test scores did not increase.
The conclusion is that better nutrition caused the score gains, but tutoring, schedule changes, and the attendance initiative are competing explanations. The correct answer describes a neighboring district that expanded tutoring and attendance efforts yet did NOT change its food — and saw no score increase. This holds the rival causes constant while removing the nutrition change, and the gains disappear, which points to nutrition as the real driver. The snack-popularity-among-athletes option is irrelevant: whether students liked the snacks says nothing about cognitive performance. The midyear teacher-replacement option actually hurts the argument, since it introduces yet another possible cause rather than ruling one out. The budget-cost option tells us the snacks were expensive, which has no bearing on whether they raised scores. The parents'-education option removes one background variable, but it never addresses tutoring, scheduling, or attendance — the specific alternatives the argument must overcome — so it offers little support. Only the neighboring-district comparison isolates nutrition, so it provides the most support.
- A university administrator argues that requiring first-year students to attend a study-skills workshop improved academic performance. She notes that the average GPA for first-year students rose from 2.9 to 3.1 in the semester after the workshop became mandatory. Attendance records show that nearly all first-year students completed the workshop, and academic advisors reported that students asked more detailed questions about time management afterward. The administrator concludes that the workshop caused the GPA increase and recommends making similar workshops mandatory for all undergraduates to raise GPAs across the university.
Which one of the following, if true, most strengthens the argument?
Answer: The grading standards for first-year courses remained the same as in the previous semester.
The administrator concludes that mandatory study-skills workshops caused first-year GPAs to rise from 2.9 to 3.1. The argument's main weakness is not ruling out alternative explanations for the GPA improvement. Answer choice E strengthens the argument by confirming that grading standards remained constant, eliminating the possibility that professors simply became more lenient. This makes the workshop a more credible explanation for the improvement. Choice B is tempting because it mentions a potentially relevant change (smaller class sizes), but this would actually weaken the argument by providing an alternative explanation for better performance. When evaluating causal claims about academic improvements, always consider whether changes in standards or expectations could account for the results.
- A gym owner argues that offering a rewards program caused members to exercise more frequently. She notes that after members began earning points redeemable for merchandise, the average number of weekly check-ins per member rose from 1.6 to 2.1. She also observes that the gym sold more water bottles and towels, which she takes as a sign that members were working out more. Therefore, she concludes that rewards programs generally increase exercise frequency and recommends that other gyms adopt similar incentives to improve member health and retention.
Which one of the following, if true, most strengthens the argument?
Answer: Members who earned the most reward points also increased their check-ins the most.
The gym owner argues that a rewards program caused members to exercise more frequently, with weekly check-ins rising from 1.6 to 2.1. The argument's key weakness is not establishing a direct connection between rewards and increased gym visits. Answer choice C strengthens this by showing that members who earned the most reward points also increased their check-ins the most—demonstrating a dose-response relationship that supports the causal claim. Choice B is tempting because it mentions new fitness classes, but this would weaken the argument by providing an alternative explanation for increased attendance. Look for proportional relationships when strengthening arguments about incentive programs: higher engagement with the incentive should correlate with greater behavioral change.
- Which one of the following, if true, most strengthens the argument?
Answer: In matched adjacent neighborhoods with similar rainfall and standing water, traps in the lemongrass areas captured far fewer mosquitoes than those in the areas without plantings.
The argument concludes that lemongrass itself drove down mosquito numbers, but the lighter-than-usual rain offers a competing explanation. The winning choice removes that competitor: by comparing matched neighborhoods with similar rainfall and standing water that differ only in whether lemongrass was planted, it isolates the plantings as the cause of the sharp trap decline. That directly strengthens the causal claim. The scent-and-pollinator observation is pleasant but says nothing about whether lemongrass reduces mosquitoes. The coincidental drainage project introduces a rival cause—fewer puddles—that actually weakens the argument by giving mosquitoes another reason to decline. The new reporting system explains why fever counts might have shifted for reasons unrelated to lemongrass, again undercutting rather than supporting the claim. Residents' objections to nonnative planting concern policy and preference, not effectiveness, so they are irrelevant to whether the plantings worked. Only the matched-neighborhood comparison rules out confounds and supports the conclusion.
- Which one of the following, if true, provides the most support for the conclusion above?
Answer: Microwear and residue patterns indicate identical manufacturing techniques, and isotope analysis traces the chert to a single quarry not used elsewhere during that century.
Strengthening questions ask which fact makes a conclusion more likely — not which one proves it. Here the conclusion is that a single dominant culture occupied the whole 300-mile basin, and the critics offer two rival explanations for the identical blades: trade or imitation.
Choice B attacks one of those branches. If microwear and residue show identical manufacturing techniques, and isotope analysis ties every blade to a single quarry used nowhere else that century, then independent communities were not copying an admired design with their own local stone. The imitation story collapses. Be honest about the limits, though: one quarry and one technique are still consistent with a single workshop trading finished blades outward. B narrows the field rather than sealing the case — and on the LSAT, narrowing the field is exactly what "most support" means. No other option helps at all.
A actively weakens the conclusion: varied pottery suggests distinct local traditions. C also weakens it by supplying the trade-and-exchange mechanism the critics wanted, among "many river communities." D restates the imitation objection in flattering language — attractive design invites independent adoption. E compares sites outside the basin from a much earlier era, so it is irrelevant on both geography and date.
Takeaway: before choosing, ask whether an option supports, weakens, or is simply off-topic — and accept the strongest partial help when perfection is not on the menu.
- Which one of the following, if true, most strengthens the argument?
Answer: Traffic counts at stores in nearby untaxed towns did not increase after the tax took effect.
D undermines the cross-border shopping alternative, supporting the claim that the tax itself drove the sales decline. The other choices are irrelevant or suggest competing explanations such as general consumption shifts or broader economic factors.
- A city's bus system introduced a mobile app that shows real-time bus arrival times. In the six months after the app launched, ridership increased by 10% compared to the prior six months. Because fares and routes remained unchanged, transit officials conclude that the app made buses more convenient and caused the ridership increase. Therefore, if the city invests in similar real-time tracking for all transit services, ridership across the entire system will increase by at least 10%, reducing traffic congestion throughout the city.
Which one of the following, if true, most strengthens the argument?
Answer: During the six months after the app launched, gasoline prices in the city did not rise substantially compared to the prior six months.
The officials claim the app caused the 10% ridership rise and will scale to the whole system. A key weakness is that some other change during those same months could explain the increase. Ruling out a rise in gasoline prices strengthens the argument by removing a competing cause: if driving got more expensive, people might have switched to buses regardless of the app, so confirming gas prices held steady makes the app the more likely cause.
The claim that some riders use the app to pick a bus stop describes how existing riders behave; it doesn't show the app drew new ridership. The download figure shows interest in the app but not that downloads translated into additional bus trips. The subway's peak-hour schedule compares two systems' timing and is irrelevant to why bus ridership rose. Improved on-time performance actually hurts the argument—it offers a rival explanation for the increase besides the app, so it fails to strengthen. Only ruling out the gas-price alternative supports the officials' causal conclusion.
- A homeowner concludes that planting native flowers caused more birds to visit her yard. She notes that in the spring after she replaced her lawn with native flowering plants, she saw noticeably more birds each morning and heard more birdsong. She also points out that the plants attracted many insects, which birds often eat. Therefore, she concludes that planting native flowers will generally increase bird populations in suburban neighborhoods, and she urges her neighbors to convert their lawns as well. Because bird activity increased soon after the planting, she treats the flowers as the main cause.
Which one of the following, if true, most strengthens the argument?
Answer: Several of the bird species she observed are known to feed heavily on insects found on native flowers.
The homeowner concludes that planting native flowers caused more birds to visit her yard, noting increased bird activity and the presence of insects that birds eat. The argument's weakness lies in not establishing a clear causal mechanism between the flowers and bird visits. Answer choice C strengthens the argument by confirming that several observed bird species actually feed heavily on insects found on native flowers—creating a direct causal pathway from flowers to insects to birds. Choice E is tempting because it mentions a neighbor's bird feeder, but this would weaken the argument by providing an alternative explanation for increased bird activity. Strengthen ecological arguments by demonstrating specific biological relationships that support the proposed causal chain.
- A chain of coffee shops introduced a new training program for baristas at 10 of its locations. Over the next two months, customer complaints at those locations dropped from an average of 12 per week to 7 per week, while complaints at the other locations stayed near 12. The company notes that the menu and prices were unchanged, so it concludes that the training program caused the improvement. Therefore, rolling out the program to every location will reduce customer complaints across the chain by roughly the same amount, even during the busiest holiday season when mistakes are most likely.
Which one of the following, if true, most strengthens the argument?
Answer: During the two months after the pilot began, the 10 pilot locations did not experience a significant drop in customer traffic compared to the other locations.
The coffee shop chain's argument concludes that a new barista training program caused customer complaints to drop from 12 to 7 per week at pilot locations, and predicts similar results chain-wide during busy holiday seasons. The argument's main weakness is that other factors could explain the improvement at the pilot locations. Choice D strengthens the argument by confirming that customer traffic didn't significantly drop at pilot locations during the test period—if fewer customers visited, that alone could account for fewer complaints regardless of training quality. Choice A is tempting because it addresses whether pilot locations were already high-performing, but this doesn't eliminate other potential causes of improvement during the specific two-month period. To strengthen causal claims, eliminate competing explanations that could produce the observed effect through different mechanisms than the proposed cause.
- Which one of the following, if true, provides the most support for the conclusion above?
Answer: Transcribed court testimonies from Valley Ridge in the 1890s already display the hallmark Region Y vowel shifts, predating widespread radio in the area.
The historian concludes the dialect came primarily from Region Y miners, while skeptics argue radio from City Z was responsible. The passage tells you that if the features appeared only after widespread radio, the migration explanation weakens. So the strongest support is evidence that the features existed BEFORE radio: the transcribed 1890s court testimonies show the Region Y vowel shifts already present, decades before radio spread. This directly undercuts the radio alternative and locates the features at the time of migration. The report that Region Y's own dialect has since shifted says nothing about when the features reached Valley Ridge. Residents moving to City Z in the 1920s runs the wrong direction and, if anything, hints at later influence rather than early migration. A standardized state curriculum by 1930 introduces a third, competing source of uniform speech and does not favor the migration story. The miners speaking several languages is background about the miners that never ties the vowel shifts to a time before radio. Only the 1890s testimonies connect timing to cause the way the conclusion requires.
- Which one of the following, if true, provides the most support for the conclusion above?
Answer: In a randomized trial, participants assigned to drink green tea daily for two weeks reported better sleep than controls, with no other lifestyle changes allowed.
The conclusion is that green tea itself improves sleep. The randomized trial with controls and no permitted lifestyle changes isolates green tea as the cause, ruling out the very confounds the critics raised. That is exactly the support the conclusion needs. The claim about caffeine sensitivity is off-target: it concerns how individuals differ, not whether green tea causes better sleep, and if anything it hints tea could hurt sleep. The black tea finding is only suggestive—it distinguishes green from black, but both groups could still share the healthy habits critics named, so it never rules out the confounds. The point about middle-aged women describes who answered the survey, not whether tea works; it addresses sampling, not causation. Noting that some green tea drinkers also used sleep-tracking apps and routines actually supplies an alternative explanation, weakening rather than strengthening the causal claim. Only the controlled trial removes the confounds and directly backs the conclusion.
- Which one of the following, if true, provides the most support for the conclusion above?
Answer: A weeklong bug randomly suppressed labels for a subset of users, and resharing of flagged posts by those users returned to pre-rollout levels while remaining low for others.
A random suppression of labels causing a rebound in reshares isolates the labels as the key factor, supporting causation. The other options either introduce confounds, report user attitudes, or describe operational changes without linking them to the observed effect.
- Which one of the following, if true, most strengthens the argument?
Answer: In a double-blind, randomized, placebo-controlled study with similar patients, those receiving Z had significantly fewer migraine days than those receiving placebo, and baseline severity and adherence were comparable across groups.
The argument claims Z itself reduces migraine frequency, but the original trial can't rule out placebo effects, natural fluctuation, or uneven adherence. The choice describing a double-blind, randomized, placebo-controlled study directly answers all of these: if Z beats placebo when severity and adherence match, the improvement is genuinely attributable to Z. That's why it most strengthens the conclusion. The choice about patients recording symptoms in phone diaries only describes how data was collected—it adds nothing about whether Z, rather than expectation or natural change, caused the improvement. The choice noting that migraine sufferers often change their diets actually reinforces a confounder the passage already raises (caffeine adjustments), so it weakens rather than strengthens. The choice citing a related compound in another open-label study repeats the same uncontrolled design flaws, so it can't rescue the causal claim. The choice stating that migraine frequency naturally decreases over time supplies an alternative explanation for the reported improvement, undermining the argument. Only the controlled trial isolates Z's effect.
- Which one of the following, if true, most strengthens the argument?
Answer: In a follow-up randomized test using the same donor segments and zip codes, adding a handwritten note increased response from 8 percent to 11 percent.
B controls for list quality by randomizing within the same segments and replicates the effect, supporting causation. A, C, D, and E are irrelevant to whether the notes caused the higher response rate.
