LSAT Quiz: Parallel Reasoning

What this quiz covers

This quiz focuses on Parallel Reasoning, 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. Whenever temperatures drop, people buy more heaters, and when people buy more heaters, hardware stores' revenue increases. A particular store's revenue increased last winter, so temperatures must have dropped. Since temperatures are outside the store's control, the store's managers should not take credit for the increased revenue. (correct answer)
2. Whenever a company advertises more, its sales increase, and when its sales increase, its revenue increases. A certain company's revenue increased last year, so it must have advertised more. Since advertising decisions are within the company's control, its executives clearly deserve credit for the increased revenue.
3. If interest rates drop, people refinance their mortgages, and if people refinance, banks' fee revenue increases. This past quarter interest rates dropped, so a certain bank's fee revenue increased. Therefore, the bank's executives should not take credit for the increased fee revenue.
4. Whenever banks' fee revenue increases, interest rates must previously have dropped. A certain bank's fee revenue increased last quarter, so interest rates must have dropped. Since rate changes are outside the bank's control, the bank should respond by lowering its fees.
5. If interest rates drop, people refinance their mortgages. Last quarter many people refinanced their mortgages, so interest rates must have dropped. Since rate changes are outside the bank's control, its executives should not take credit for the wave of refinancing.

Explanation: The advisor's argument runs a two-link chain (rates drop → refinancing → higher fee revenue), then observes the last effect, works backward to infer the first cause, and concludes executives deserve no credit because that cause is beyond their control. The heater argument matches every step: two links (cold → heater buying → higher store revenue), an observed revenue increase, a backward inference to cold weather, and a no-credit conclusion resting on an uncontrollable external cause. The advertising argument reverses the credit conclusion—it says executives DO deserve credit because the cause (advertising) is within their control—so its final move is the opposite of the original's. The 'interest rates dropped, so revenue increased' argument reasons forward from cause to effect rather than backward from effect to cause, breaking the parallel structure. The 'whenever fee revenue increases, rates must have dropped' argument starts from only a single conditional and ends with a policy recommendation to lower fees, not a no-credit judgment. The final option uses just one link and observes refinancing directly rather than working back from fee revenue, so its chain is shorter and its inferred fact differs. Only the heater argument reproduces the full pattern.

Question 2

1. A tech reviewer claims a new keyboard increases typing speed. In an informal poll, most buyers reported feeling less fatigued while typing. The reviewer reasons that feeling less fatigued is a sign of increased typing speed, and that people are generally accurate about changes in their own performance. Therefore, since most buyers reported less fatigue, the keyboard increases typing speed. (correct answer)
2. A doctor claims a new medication reduces pain. In a small clinical review, most patients reported feeling less pain after taking it. The doctor reasons that reported pain is itself the measure of actual pain, and that patients are the best judges of their own discomfort. Therefore, since most patients reported less pain, the medication reduces pain.
3. A coach claims a new training plan improves endurance. In a series of timed trials, most athletes ran measurably longer distances after adopting it. The coach reasons that a longer distance run in a fixed time directly demonstrates greater endurance, without relying on how the athletes felt. Therefore, since most athletes ran farther, the plan improves endurance.
4. A columnist claims a new language app improves fluency. In an informal survey, most users reported enjoying the daily lessons more than before. The columnist reasons that enjoyment is not a reliable sign of fluency, and that pleasant lessons can accompany little actual progress. Therefore, since enjoyment does not track fluency, the reports fail to support the claim.
5. A scientist claims a pill improves memory. In an informal survey, most users reported feeling more focused after taking it. The scientist reasons that people are often inaccurate about changes in their own mental performance, and that such self-reports are therefore unreliable. Therefore, despite the reports of feeling focused, the pill probably does not improve memory.

Explanation: The original argument makes a specific chain of moves: it takes a subjective feeling (users feel more focused), treats that feeling as a sign of an objective benefit (better memory), assumes people accurately judge their own mental performance, and concludes the product works. Look for the choice that repeats all four moves. The keyboard argument does exactly this: buyers feel less fatigued, that feeling is treated as a sign of faster typing, people are assumed accurate about their own performance, and the product is declared effective. The pain-medication choice differs because reported pain isn't merely a 'sign' of pain—it is the direct measure of pain, so there is no questionable leap from feeling to a separate benefit. The endurance choice relies on an objective measurement (distance run in fixed time), explicitly not on how athletes felt, so it doesn't equate a subjective feeling with a benefit. The language-app choice reaches the opposite conclusion: it rejects the self-reports as evidence rather than accepting them. The memory-pill choice also runs the reasoning in reverse, calling self-reports unreliable and concluding the pill does not work. Only the keyboard argument mirrors both the flawed structure and the accepting conclusion of the original.

Question 3

1. All licensed electricians must complete a supervised apprenticeship before working. Daria completed a supervised apprenticeship this year, so she is now a licensed electrician.
2. All certified lifeguards must pass a swim test annually. Marco did not pass the swim test this year, so he is not currently a certified lifeguard. (correct answer)
3. Only certified lifeguards are permitted to pass the annual swim test; Marco did not pass the test this year, so Marco is not a certified lifeguard.
4. All certified lifeguards must pass a swim test annually. Marco passed the swim test this year, so Marco is therefore a currently certified lifeguard.
5. No certified lifeguards ever fail the swim test in any year. Marco failed the swim test this year, so Marco must genuinely dislike swimming.

Explanation: The argument runs: all A must be B; Victor is not B; therefore Victor is not A. This is valid modus tollens. The lifeguard version that says all certified lifeguards must pass the annual swim test, that Marco did not pass, and therefore that Marco is not currently certified matches that structure exactly. The electrician version reverses the conditional: completing an apprenticeship is required for licensing, but doing it does not guarantee a license — that is affirming the consequent. The 'only certified lifeguards pass the swim test' version wrongly treats passing as something only the certified may do, reversing which group the requirement restricts. The version where Marco passed and is therefore certified again affirms the consequent: passing is necessary, not sufficient. The final version starts from an absolute ('no certified lifeguards ever fail') but then draws a conclusion about disliking swimming, which the premises never address. Only the second option preserves the valid 'all A are B; not B; so not A' form.

Question 4

1. A team owner argues the team should not hire a new trainer. Last year, when the team hired a trainer, injuries decreased. But the owner claims injuries were going to decrease anyway because the schedule became less demanding. Since the schedule is not expected to be less demanding this year, hiring a trainer this year would not decrease injuries. Therefore, the team should not hire one. (correct answer)
2. A director argues the company should hire a new consultant because profits rose sharply last year after one was hired. But the director claims profits were going to rise anyway because the regional market expanded. Since the market is expected to expand again this year, hiring a consultant this year would raise profits even further. Therefore, the company should certainly hire one.
3. A council member argues the city should not build a new playground. Last year, when the city built one, property values rose steadily. But the member claims values were going to rise regardless because the local school district improved. Since values are already unusually high, the city simply cannot afford another rise this year. Therefore, the city should not build one.
4. A manager argues the firm should not hire a new recruiter. Last year, when the firm hired one, its hiring increased. But the manager claims hiring was going to increase anyway because of the company's rapid expansion. Since the firm is expected to expand again this year, hiring a recruiter this year would not help much. Therefore, the firm should not hire one.
5. A principal argues the school should not adopt a new curriculum. Last year, when the school adopted one, test scores rose noticeably. But the principal claims the curriculum itself caused the rise, and because it clearly helped before, it will surely help again. Since it worked once, adopting it again would raise scores. Therefore, the school should not adopt it.

Explanation: The original reasoning says: the action seemed to work before, but only because of an outside condition; that condition won't recur, so the action won't help, so don't repeat it. The trainer argument matches perfectly—injuries fell only because the schedule eased, the schedule won't ease again, so hiring a trainer won't help, so don't hire. The consultant argument favors hiring and says the helpful condition (market expansion) WILL return, drawing the opposite conclusion and treating the external factor the opposite way. The playground argument names an outside cause but then swaps in a different reason for its conclusion (values are already high, another rise is unaffordable) instead of the condition failing to recur. The recruiter argument credits expansion for last year's success but then says expansion WILL happen again, making its 'won't help' conclusion inconsistent—the external condition here does recur, unlike the original. The curriculum argument accepts that the curriculum itself caused the rise and will help again, so its conclusion against adopting flatly contradicts its own premises. Only the trainer argument keeps both the correlation-versus-causation move and the non-recurring external condition.

Question 5

1. Every ingredient in this salad is low in calories, including the dressing and croutons; therefore the salad as a whole must be low in calories, so it can be marketed as a diet option. (correct answer)
2. This hearty stew is undeniably low in calories overall; thus each of its individual ingredients, including the broth and the potatoes, must also be low in calories.
3. Most components of this sofa are lightweight, including its cushions and its frame; therefore the sofa as a whole is definitely easy for one person to lift and carry.
4. The aluminum frame of this bicycle is quite light; therefore the whole bicycle must be light, even though its wheels and its motor are both notably heavy.
5. Each part of this table is genuinely heavy on its own; nevertheless, once fully assembled the table feels surprisingly light because its weight is so evenly balanced.

Explanation: The passage commits a composition fallacy: it assumes that because every individual part is light, the whole assembled speaker must be light too. The salad choice mirrors this exactly, reasoning that because every ingredient is low in calories, the whole salad must be low in calories. That is the same part-to-whole leap. The stew choice runs the reasoning backward: it moves from a property of the whole (low-calorie stew) to a property of each part, which is a division fallacy, not composition. The sofa choice weakens the premise to 'most' components rather than all, so its certain conclusion is not supported the same way the passage's is. The bicycle choice draws its conclusion from only one part (the frame) while explicitly admitting other parts are heavy, so it does not reason from every part being light. The table choice actually denies the composition pattern, granting that each heavy part yields a light-feeling whole. Only the salad choice reproduces the every-part-therefore-whole structure of the original.

Question 6

1. The two chess clubs must be using the same coaching method. Both have produced players who win regional tournaments at an unusual rate, and neither club draws its members from any special pool of talent. Similar results in an activity of this kind are not likely to arise from dissimilar instruction.
2. Any photographic negative stored above twenty degrees for more than a decade develops a haze that no cleaning removes. The negatives in the studio's basement drawer sat at twenty-four degrees for fifteen years, and none of them has ever been cleaned. Those negatives, therefore, carry a haze that cannot be removed.
3. Two irrigation ditches were dug to the same depth, in the same soil, at the same gradient. How quickly a ditch silts up is determined entirely by depth, soil, and gradient. The first ditch silted up in three seasons; the second, it follows, will silt up in three seasons as well.
4. The Aubrey Quartet's recordings will sell briskly in independent shops. The ensemble records for the same label as the Lindorf Quartet, performs repertoire of the same period, and is promoted by the same publicist, and neither ensemble tours outside the region. Lindorf's recordings sell briskly in precisely those shops. (correct answer)
5. The Route 9 bus and the Route 12 bus keep the same schedule, use identical vehicles, and charge the same fare, and neither route has been rerouted this year. Route 12, however, passes through the river tunnel, where delays are frequent. Route 9 will therefore not run late as often as Route 12.

Explanation: Abstract form: two cases share several enumerated respects, plus a statement that neither has some additional advantage; one case is known to have a further property; the conclusion transfers that property to the other case. The argument is flawed because nothing establishes that the enumerated respects are the ones that determine the property. Choice D instantiates the form precisely — shared label, shared repertoire period, shared publicist, neither touring, one ensemble's recordings sell briskly, therefore the other's will — with the conclusion stated first rather than last. Distractors diverge structurally as follows.

Question 7

1. A trade journal reports that most alloys cast without flux crack within a decade of casting. The bracket mounted above the workshop bench was cast without flux some thirty years ago, has never been recast or reinforced, and shows no crack anywhere along its length. The journal's report is therefore mistaken.
2. A gardening guide states that no bulb planted after November flowers the following spring. One bulb in the west border was planted in the first week of December and produced no flower at all that spring, and it was neither dug up nor moved in the interval. The guide's statement is therefore correct.
3. The claim in the finisher's manual that no varnish applied in humid air cures evenly is mistaken. A table varnished last August in the dry back workshop cured perfectly evenly, its surface has never been refinished, and the shop's daybook confirms both the date and the conditions of the work.
4. The seed manual states that any lot stored above thirty percent humidity loses its viability within two years. The lot in the north shed sat at thirty-five percent humidity for three years and was never dried out, so it has lost its viability, whatever its outward appearance may suggest.
5. The binder's manual is wrong to claim that no adhesive applied without heat will hold a spine for fifty years. A ledger in the county office has a spine still intact after eighty years, shows no sign of repair, and the binder's own notes record that its adhesive was applied cold. (correct answer)

Explanation: Abstract form: a universal negative claim (nothing satisfying condition C has property P) is met with a single case that both satisfies C and possesses P, together with a premise ruling out an alternative explanation of P; conclusion, the universal claim is false. A single genuine instance does refute a universal claim, so the reasoning is sound. Choice E instantiates it: the manual's universal claim about heatless adhesive, one ledger whose spine has lasted eighty years, no repairs to explain the durability away, and documentation that the adhesive was in fact applied cold — with the conclusion stated first. Distractors diverge structurally as follows.

Question 8

1. The installation of the new streetlights along the main roads is what reduced the town's insect population. The insect count fell sharply during the year following the installation, and no other change in the town's practices or surroundings occurred during that year, so far as the council was able to determine.
2. Volunteers at the ceramics studio were assigned at random either to receive a weekly bulletin on glazing techniques or to receive no bulletin at all. Those who received the bulletin afterward logged more hours at the studio's wheels than the others did. Receiving the bulletin, then, increased the hours volunteers spent at the wheels.
3. The narrow street grids laid out centuries ago account for two features that certain districts commonly display together. Such districts tend to have both a large number of public drinking fountains and a large number of open-air markets. Neither of those two features, however, plausibly brings about the other.
4. Diners who order the tasting menu at a certain restaurant remain at their tables roughly forty minutes longer than diners ordering from the standard card. The tables assigned to the two groups are of similar size. Ordering the tasting menu, it follows, causes a diner to extend the visit. (correct answer)
5. Residents of a certain apartment block who own pianos report knowing more of their neighbors by name than residents who own no piano, and the two groups have lived in the building for equally long periods. Any given piano-owning resident, therefore, knows more neighbors by name than any given resident without one.

Explanation: Abstract form: two self-selected groups are found to differ in an outcome; the argument notes that the groups match on one further variable; it concludes that the trait defining group membership causes the outcome. This is invalid because self-selection leaves the reverse direction open — those already inclined toward the outcome may be the ones who take on the trait. Choice D instantiates exactly this: diners choosing the tasting menu linger longer, table size is matched, and the choice of menu is declared the cause of the longer visit, though diners planning a leisurely visit may be the ones who choose that menu. A reasons from a single before-and-after sequence in one location, not from a comparison of two contemporaneous groups, so no self-selection step exists. B assigns membership at random, which closes off the reverse direction and makes the causal inference sound rather than parallel. C explicitly denies that either correlated feature causes the other and posits a common cause instead, the opposite inferential move. E draws no causal conclusion at all, instead projecting a group-average difference onto any arbitrary individual member.

Question 9

1. The kiln at the Harrow pottery will require relining next year. Kilns of the Verrick model invariably require relining in their fifteenth year of use, and the Harrow kiln, a Verrick model that has been fired nearly every day since its installation, is now in its fourteenth year.
2. The two municipal clock towers house escapement mechanisms of identical construction and were wound on the same schedule by the same custodian for decades. The mechanism in the north tower jammed during its twentieth year. That identical construction, therefore, is what caused the north tower's mechanism to jam.
3. Every press in the workshop will need new rollers in its ninth year of use. The Ludlow press runs on the same paper stock and the same ink as the other presses do, and it is given press runs of comparable length; it needed new rollers in exactly its ninth year of use. All the presses stand in one room.
4. Most of the seventy lampposts that the borough installed in a single season had to be rewired before their thirtieth year. The lamppost on Peel Street was installed during that season and has been maintained on the borough's standard schedule ever since. It probably had to be rewired before its thirtieth year.
5. Two greenhouses at the botanical station were glazed with the same panels, share a ventilation design, and are watered on one schedule. The eastern greenhouse had its panels replaced in its twelfth season. The western greenhouse, now in its eleventh season, will need replacement panels next season. Both stand on the same exposed ridge. (correct answer)

Explanation: Abstract form: two particular items share several enumerated features; one of them underwent a particular event at a given age; therefore the other will undergo that event upon reaching the same age. The flaw is treating a single occurrence in one item as a schedule projectable onto a similar item. Choice E reproduces this precisely: two greenhouses share glazing, ventilation, and watering; one needed new panels in its twelfth season; the other, in its eleventh, is said to need them next season, with a further shared feature appended after the conclusion, as in the original. A applies a stipulated universal rule about a model of kiln to an instance, which is deductively valid and hence not parallel. B stops at an explanatory claim about why the known case failed rather than projecting the outcome onto the second case. C moves from a single instance to a universal claim about every member of a class, not from one case to one similar case. D applies a statistical generalization about a large group to a member of that group, a different inferential species altogether.

Question 10

1. The trustees acted properly in awarding this year's fellowship. Trustees act properly only if the criteria for the award are published before applications open, and these criteria appeared in the society's bulletin a full month before the application period began, as the secretary's file confirms.
2. An auctioneer behaves improperly whenever he places a bid on a lot in a sale that he is himself conducting, however fair the price finally realized may be. Merrow, who conducted last week's sale at the county rooms and catalogued the disputed lot himself, advised a friend seated in the room on what to bid. Merrow therefore behaved improperly.
3. The inspector held no lease on any building she surveyed last quarter. An inspector who holds a lease on a building she surveys thereby files a defective report, and the reports she filed last quarter were all reviewed by the borough office and found to be sound.
4. Archivists generally act improperly in lending original documents to private collectors, though a good deal depends on the terms of the particular loan. Pell lent three original letters from the Wrenford papers to a collector last spring. Pell's conduct on that occasion was therefore certainly improper.
5. A referee acts improperly in officiating a match in which a club he once coached is playing, no matter how even-handed his decisions during the match prove to be. Ferris officiated Saturday's fixture between two clubs, one of which he had coached three seasons earlier. Ferris therefore acted improperly. (correct answer)

Explanation: Abstract form: a principle states a sufficient condition for a verdict of impropriety and expressly sets aside a mitigating feature as irrelevant; the case at hand is shown to satisfy that sufficient condition; the verdict is therefore drawn. Choice E instantiates it: officiating a match involving a club one has coached is declared improper irrespective of the even-handedness of the decisions, Ferris did exactly that, and the verdict follows. A relies on a principle stating a necessary condition for propriety and treats its satisfaction as sufficient, an invalid move. B states a principle whose triggering condition is placing a bid, but the case describes advising another person's bid, so the case is never shown to fall under the principle. C reasons from the absence of the principle's consequence back to the absence of its triggering condition, the contrapositive direction rather than direct application. D applies a hedged generalization admitting of exceptions and yet issues a categorical verdict, a strengthening the premise does not license.

Question 11

1. Both features, according to the innkeepers' guild, stem from a lodge's proximity to the main highway. Valley lodges that offer evening shuttle service do tend to fill their rooms earlier in the season than lodges without shuttles, and the guild's census recorded highway distance for every lodge in the valley.
2. Greenhouse operators who moved half their seedling trays into clay pots while leaving the rest in plastic found that the clay-potted seedlings survived transplanting more often, all other conditions being held constant. Clay pots improve transplant survival, the growers' bulletin concludes; every tray in the trial was tracked to the end.
3. Chess clubs in the province that retain a paid coach post better tournament results than clubs without one, and no other organizational difference between the groups was noted. Strong tournament results, the provincial federation concludes, lead clubs to retain paid coaches; the federation's review took in every registered club.
4. The corrosion on the Ferndale bridge railings was caused by road salt, the county engineer concluded. Prolonged exposure to road salt is already known to corrode steel railings of that type, and the Ferndale railings were salted heavily for six winters; no other bridge in the county was examined.
5. The regulator has found the northern lakes' ferry operators alike in fleet and route, differing only in how they publish schedules. Operators issuing printed timetables carry a larger share of commuters than those posting schedules online only. Printing timetables, the regulator concludes, raises an operator's commuter share; every licensed operator was reviewed. (correct answer)

Explanation: Abstractly: two subgroups of a population differ in feature X and also differ in outcome Y; no third difference was recorded; therefore X causes Y — an inference from correlation to causation in a stated direction, buttressed only by an exhaustiveness remark about coverage, which does nothing to rule out reversed causation. Choice E instantiates exactly this: operators alike in all recorded respects but schedule format differ in commuter share, so schedule format is said to raise commuter share, with the same exhaustive-coverage remark; the possibility that high-commuter operators are the ones that print timetables is untouched. A concludes that both correlated features arise from a third factor rather than that one produces the other. B rests on a within-operation controlled comparison in which the factor was manipulated, so the correlation-to-causation gap is closed and the argument is not parallel. C concludes that the outcome causes the feature, reversing the direction of the stimulus's inference. D applies an already-established causal generalization to a particular case rather than inferring a causal relation from a correlation.

Question 12

1. Every department's allocation in the city budget must be balanced. The auditor certified last month that the budget as a whole is balanced, and a budget is nothing but the allocations composing it, though the certification did not examine departments one by one.
2. None of the four crates in the shipment weighs more than twenty kilograms, and a shipment's weight is simply the sum of its crates' weights. The freight clerk therefore records the shipment as weighing under eighty kilograms, noting that the crates have never been placed on the scale together.
3. Twenty of the two hundred film reels in the archive were unwound and inspected, each proving free of decay; a conservator carried out the inspection over two afternoons. The archivist concludes that no reel in the collection is decayed, granting that the remaining reels stay in their cans.
4. Read on its own, each clause of the drafted lease is unambiguous, a judgment two solicitors reached independently. A lease is nothing more than its clauses. The arbitrator accordingly treats the lease as unambiguous overall, granting that no one has yet considered how the clauses bear on one another. (correct answer)
5. The coastal trail as a whole is passable in early spring, the hiking club has announced. Most of its segments were confirmed passable by the ranger's patrol last week, and a trail is nothing but its segments, though a few segments went unpatrolled this year.

Explanation: Abstractly: every part taken in isolation has property P; the whole is composed of nothing but those parts; therefore the whole has P — a composition inference concerning a property that need not survive aggregation, with an explicit concession that the parts' joint operation is untested. Choice D reproduces this: each clause read alone is unambiguous, a lease is nothing but its clauses, so the lease is unambiguous, with the parallel concession that the clauses' interaction has not been examined. A runs the inference in the opposite direction, from a property of the whole to a property of each part. B concerns a property that aggregates arithmetically, so the conclusion actually follows from the premises and the pattern is valid rather than flawed. C generalizes from an inspected sample to the uninspected remainder, which is statistical rather than part-to-whole composition. E establishes the property only for most parts, adding a quantitative gap the stimulus does not have.

Question 13

1. A tree on municipal land may be removed only if it is diseased and a licensed arborist has inspected it. The elm on Garner Street has been inspected by a licensed arborist and is, all agree, diseased. The works department may therefore remove it; the elm was planted in 1954 and stands near a bus shelter.
2. Under the conservatory's rules a scholarship must be renewed when the holder has maintained a first-class average and has performed in two public recitals. Ms. Oyelaran's average this year was first class, and her teacher speaks warmly of her progress. The committee has concluded that her scholarship must be renewed.
3. Under the league's rules a match result must be voided if the referee lacked current certification and a formal protest is lodged within seven days. Both clubs agree the referee at Saturday's match held no current certification, and the visiting club lodged its protest on Monday. Saturday's result must therefore be voided. (correct answer)
4. A refund is proper if the cancellation lay within the carrier's control and the claim was filed within thirty days. The passengers' advocate, reviewing last Tuesday's canceled flight, notes that the refund granted was proper and concludes that the cancellation lay within the carrier's control and the claim was timely.
5. In each of the four disputes the journal has settled, an article was retracted when its data could not be reproduced and a co-author had objected to publication. The editorial board therefore adopts as its standing rule that any article answering to both descriptions is to be retracted, whatever its field.

Explanation: Abstractly: a principle states that whenever two conditions jointly obtain, a certain action is called for; both conditions are established of a particular case; therefore the action is called for in that case — a valid application of a sufficient condition, with an inert detail attached. Choice C instantiates the form: voiding is required if the referee was uncertified and a protest is timely; both are established of Saturday's match; therefore the result must be voided. A states the two conditions as necessary rather than sufficient and then treats their satisfaction as licensing the action, so a valid form is replaced by a necessary-for-sufficient substitution. B establishes only one of the principle's two conditions, leaving the application incomplete. D moves backward, from the action's being proper to the conclusion that the principle's conditions obtained. E argues from particular settled cases to the general principle itself, reversing the direction of the stimulus, which applies a principle already in hand.

Question 14

1. Rowing clubs that train on still water post faster race times than clubs training on tidal water. Since still-water clubs also tend to be the larger ones, an analyst compared clubs of equal membership, and the still-water advantage persisted within every size band, which the analyst had not expected. Training on still water therefore improves a club's race times.
2. Couriers who carry parcels in rigid panniers complete more deliveries per shift than couriers using soft satchels. The pannier users are, it is true, the firm's longest-serving employees. Still, that fact leaves the pattern untouched, and the pattern appears in every quarterly report. Rigid panniers therefore raise a courier's delivery rate. (correct answer)
3. Villages in the valley that maintain many bell towers also hold many summer fairs. Neither practice could plausibly produce the other. Both, then, most likely trace to a single earlier source: the medieval guild endowments that paid for civic building and civic festivity alike, records of which survive in the county archive.
4. Among the region's weavers, those working at hand looms take home prizes more often than those working at power looms, and the gap has held for decades in the guild's tallies. A hand-loom weaver entering next year's show is therefore likelier to win a prize than a power-loom weaver is.
5. Ferries that load vehicles through a stern ramp report fewer boarding delays than ferries loading amidships, according to harbor authority logs covering eleven routes. Stern loading must therefore reduce boarding delays, and any operator that wants shorter boarding times should have its vessels refitted with stern ramps.

Explanation: Abstract form: a correlation between practice X and outcome Y is reported; a confounding feature of the X-adopters is conceded; the concession is set aside on the ground that the correlation itself survives and recurs; the conclusion is that X causes Y. The flaw is that the conceded feature could explain the correlation, which persists whether or not X is causal. (B) instantiates this exactly: rigid panniers correlate with higher delivery counts, the longer tenure of pannier users is conceded, that concession is brushed aside because the pattern recurs in every report, and rigid panniers are declared to raise the delivery rate. (A) actually neutralizes the conceded factor by comparing clubs of equal size, so its causal conclusion is supported rather than fallacious. (C) infers a shared antecedent cause for two correlated practices instead of inferring that one correlate causes the other. (D) draws only a further probabilistic prediction from the correlation and asserts no causal claim at all. (E) omits the concession-and-dismissal move and appends a second inferential step, a practical recommendation derived from the causal claim.

Question 15

1. Every seed lot supplied by the Corbin nursery was treated with a copper wash, and every copper-washed lot germinates within nine days of sowing. The lot sown in the west field last week came from Corbin, whose invoices the farm keeps on file. That lot will therefore germinate within nine days.
2. No cider pressed at the Marlow works was ever bottled in green glass, and every cask stamped "M-line" held cider pressed at those works. The sealed cask still standing in the cellar, whose label has faded, was not bottled in green glass. That cask, then, is stamped "M-line," though the cellar book lists nine casks in all.
3. The bell in the north tower was not cast by the Verrier foundry. Every bell that foundry cast was tuned to the old civic pitch, and no bell tuned to that pitch sounds the A-flat now heard from the tower — and the tower's bell, as any listener can confirm, sounds an A-flat. (correct answer)
4. The tile lifted from the chapel floor during last year's repairs was not fired in the Sandway kiln. Most tiles fired at Sandway contain crushed shell, and no tile containing crushed shell resists frost; this tile resists frost, as the mason demonstrated. The repairs took a fortnight.
5. Every violin varnished in the Cremona manner has a reddish ground, and no reddish ground fluoresces green under ultraviolet light. The instrument acquired last season, whose label is illegible, was varnished in the Cremona manner. Its ground therefore does not fluoresce green.

Explanation: Abstract form: all A are B; no B is C; the particular case x is C; therefore x is not A. This is a valid exclusion run backward to deny category membership. (C) instantiates it: all Verrier bells are old-pitch bells (all A are B); no old-pitch bell sounds A-flat (no B is C); the north tower's bell sounds A-flat (x is C); therefore it is not a Verrier bell (x is not A). (A) chains two affirmative universals to place the case in a further category, reaching a positive conclusion rather than denying membership. (B) argues from the case's lacking the excluded property to its membership in the category, which does not follow. (D) weakens the first premise to "most," so the exclusion cannot rule out membership. (E) runs the exclusion forward — the case is in category A, so it lacks C — instead of using possession of C to deny that the case is in A.

Question 16

1. Ferreira was obliged to declare her tie to the grain contract. The cooperative's rules oblige a member to declare any tie that other members could reasonably think apt to sway her vote, actual swaying being no part of the test; and Ferreira's vote was in fact swayed by her cousin's stake.
2. The conservatory's rules require a jury member to withdraw from any audition at which a former pupil of hers performs; whether she recognizes the pupil does not matter. No former pupil of Okafor performed at Tuesday's audition, at which the jury heard eleven candidates. Okafor was accordingly not required to withdraw.
3. Any exhibit lent from abroad must be insured at replacement value, and any exhibit so insured must be photographed before installation. The bronze horse arriving next month is lent from a Lisbon collection, and the gallery's registrar handles both steps. The horse must therefore be photographed before it is installed, though the loan agreement mentions no photography.
4. Halvorsen almost certainly stepped aside when the mill came up for audit last quarter. Auditors who have had prior dealings with a firm nearly always step aside in such cases, as the professional body's surveys confirm, and Halvorsen had had prior dealings with that mill. The audit closed on time.
5. Under the building's bylaws a tenant must notify the association of any alteration that neighbors could reasonably regard as affecting shared structure; actual effect is immaterial. Duval removed a partition wall in March. Neighbors could reasonably regard that removal as affecting shared structure, so Duval had to notify the association. (correct answer)

Explanation: Abstract form: a rule imposes a requirement on anyone meeting condition C, with an explicit statement that a related matter E is irrelevant to the requirement; the particular agent's situation is shown to meet C; therefore that agent was required to act. The conclusion follows. (E) instantiates it: the bylaw requires notification of any alteration neighbors could reasonably regard as affecting shared structure, actual effect being immaterial; Duval's removal is something neighbors could reasonably so regard; therefore Duval was required to notify. (A) establishes only that the vote was in fact swayed — precisely the matter the rule declares irrelevant — and never shows the triggering condition satisfied. (B) infers the absence of the requirement from the absence of the triggering condition, treating a sufficient condition as necessary. (C) chains two rules, adding an inferential link the stimulus's single application lacks. (D) applies a statistical generalization to predict what an agent probably did rather than deriving what an agent was required to do.

Question 17

1. Field guides are mistaken in asserting that every alpine gentian blooms only after the snowpack around it has melted entirely. On Mount Carrow's south ridge, botanists recorded a colony of alpine gentians in full bloom while snow still lay across the slope. The claim remains a serviceable approximation for most colonies. (correct answer)
2. Numismatic handbooks state that every coin struck at the Larch Hill mint bears a small crescent below the date. A coin in the Farrow collection that lacks that crescent has now been authenticated as a genuine issue of the same period, though its surfaces are badly worn. So the handbooks' rule is mistaken.
3. Guidebooks to timber framing are wrong to say that oak pegs typically outlast the beams they join. In one restored barn near Halvers, dated to 1790, the oak pegs had failed while the surrounding beams remained sound — a case the guidebooks nowhere acknowledge, though they are otherwise reliable.
4. Every ledger kept by the Weald Company between 1880 and 1900 was bound in green buckram, according to the company's own inventory. The volume recently acquired by the county archive is a Weald ledger of 1893, catalogued as such. That volume, then, is bound in green buckram, whatever its present condition.
5. Treatises on glassblowing assert that every furnace of the Vitraro pattern was fired with charcoal. Yet no surviving record of any Vitraro furnace mentions its fuel at all, so nothing whatever confirms the treatises on this point. The assertion should therefore be regarded as false, however long it has gone unchallenged.

Explanation: Abstract form of the stimulus: a body of authorities asserts an unhedged universal claim, that every X (enforceable ordinance) has property P (prior publication in the gazette); one case is established both to fall under the subject class — the Ellsworth ordinance is enforceable, as the courts' continued enforcement shows — and to lack P; the claim is therefore false, with a concession that it still serves as a rough guide. The inference is valid: a single genuine counterinstance refutes an unhedged universal. Choice A instantiates the same form: field guides assert a universal claim about every alpine gentian; a recorded colony is established to be alpine gentians and to have bloomed while snow remained, contrary to the claim; the claim is pronounced mistaken, with the parallel concession that it approximates most colonies. The other choices diverge structurally: B's cited case is never shown to belong to the class the generalization is about; C attacks a claim explicitly hedged as holding 'typically,' which a single exception cannot refute; D runs the inference in the opposite direction, applying the generalization to a case rather than refuting it; E rejects the universal claim for want of confirming evidence instead of producing a counterinstance.

Question 18

1. Seedlings in the north greenhouse were given filtered water; those in the south greenhouse, ordinary tap water. All other conditions were held identical by the staff. The filtered-water seedlings grew noticeably taller, so filtered water promotes seedling growth. Chance is not a plausible explanation, since thousands of seedlings were involved.
2. Villages that hold an annual summer fair usually also have well-maintained footpaths. It would be hasty, however, to conclude that holding a fair leads to path maintenance. In nearly every such village there is an active volunteer association, and it is that association which both organizes the fair each August and repairs the paths.
3. Printing a new menu each morning must make a restaurant's ingredients fresher. Reviewers last year praised ingredient freshness far more often at restaurants that reprint daily than at those with fixed menus. Sampling accident is not a credible explanation, since over four hundred restaurants were reviewed. (correct answer)
4. Most cyclists in the province ride daily. In a poll of a thousand cyclists in the province, almost two-thirds said that they ride every day, and cyclists who ride less often had no reason to avoid the poll. The result cannot be attributed to sampling error, given the number of respondents.
5. When the archive replaced the fluorescent bulbs in its reading room with incandescent ones, staff made fewer transcription errors during long shifts. Incandescent lighting therefore reduces transcription errors. The improvement was not illusory, since the supervisor tallied errors both before and after the change was made.

Explanation: Abstract form: among many observed cases, a feature of the setting (F) is correlated with a favorable quality (Q); the argument concludes that F causes Q, and defends the causal claim only by ruling out coincidence on the strength of the large sample. The inference is flawed because the causal direction could run the other way — the cases already possessing Q may be the ones that acquire F. Choice C instantiates exactly this: daily menu reprinting (F) is correlated with praise for ingredient freshness (Q) across four hundred reviewed restaurants; the conclusion is that F causes Q, with chance dismissed by appeal to the number of cases; and the correlation is equally well explained in reverse, since restaurants whose ingredients are freshest are the ones whose menus must change daily. Choice A supports its causal claim with a comparison in which all other conditions were held identical, so it is not an uncontrolled correlation and is not vulnerable in the same way. Choice B moves in the opposite direction, denying causation by locating a common cause. Choice D draws no causal conclusion at all, generalizing a frequency from a sample to a population. Choice E infers a cause from a single before-and-after change in one location rather than from a correlation across many cases.

Question 19

1. The new alloy used in the cookware conducts heat extremely well. Any substance that conducts heat extremely well can be used for saucepans. The alloy is a mixture of four metals; each of those four metals, then, can be used for saucepans, since each is a constituent of the alloy.
2. Every page of the club's ledger bears the treasurer's signature. Any document page bearing that signature has been authenticated under the club's rules, which were adopted in 1954. Therefore each page of the ledger has been authenticated, whatever an outside auditor may later decide about the ledger.
3. The anthology, reissued last spring, is suitable for radio play between news bulletins. Most of its tracks last less than two minutes, and any recording lasting less than two minutes is suitable for such play according to the station's programming guide. That guide has been in use since the station's founding.
4. A single volunteer will be able to carry the entire exhibit stand. The stand is made up of twelve panels, and no panel weighs more than three kilograms. Anything weighing no more than three kilograms can be carried by one person. The panels were donated by a local printing firm. (correct answer)
5. A hedge maze is easy for visitors to navigate only if every junction within it is signposted. Every junction in the maze at the country house, which was planted just three years ago, is signposted, and the gardeners inspect the signs weekly. The maze is thus easy for visitors to navigate.

Explanation: Abstract form: every part of a whole possesses feature F; anything possessing F also possesses property Q; therefore the whole itself possesses Q. The inference is an invalid composition, since Q may hold of each part without holding of the aggregate of all the parts. Choice D reproduces it precisely: each of the twelve panels weighs under the stated limit; anything under that limit is carryable by one person; therefore the whole stand, composed of all twelve, is carryable by one person — the property is illicitly transferred from every part to the aggregate. Choice A runs the inference in the opposite direction, from a feature of the whole alloy to a property of each constituent metal. Choice B never leaves the level of the parts: its conclusion is about each page rather than about the ledger as a whole, and it is therefore valid. Choice C attributes the relevant feature only to most of the parts rather than to each, so its composition step rests on a weaker premise than the stimulus's. Choice E treats a stated necessary condition for a property as sufficient for it, a conditional error rather than a part-to-whole one.

Question 20

1. The volume the visiting scholar produced is not held in the rare-book room, the librarian has concluded. Every ledger held in that room has been catalogued, everything catalogued there carries a stamped accession number, and this volume carries no such number, whatever its binding suggests.
2. Every dog certified for alpine rescue has completed the avalanche drills, and every dog that has completed those drills responds reliably to hand signals. Kessel, a shepherd mix acquired two winters ago, is certified for alpine rescue, so the training director expects that Kessel responds to hand signals.
3. A policy lapses whenever its holder misses two consecutive premium payments. The Ndlovu policy has lapsed, and so the insurer's clerk, working from the file alone, has recorded that the holder missed two consecutive payments during the last quarter, though the file notes other irregularities as well.
4. Tarrant cannot interpret regression output, the registrar reports. Every student admitted to the advanced seminar has completed the statistics course, and everyone completing that course can interpret regression output; Tarrant, a second-year student, was not admitted to the seminar this term.
5. Every apprentice admitted to the guild's forge program has passed the metallurgy examination, and everyone who has passed that examination can read technical drawings. Peraza, hired last spring, can read technical drawings. The guild's registrar has inferred that Peraza was admitted to the forge program. (correct answer)

Explanation: Abstractly: all A are B, all B are C, and a particular item has C; the argument concludes that the item is an A — running a two-link chain backwards from the final consequent to the initial antecedent. Choice E does precisely this: admission implies passing the examination, passing implies reading technical drawings, Peraza reads technical drawings, so Peraza is said to have been admitted. A traverses the same two links contrapositively from the denial of C to the denial of A, which is valid. B traverses the chain forward from a case that is A to the conclusion that it is C, also valid. C reverses only a single conditional rather than a chain of two, so the number of inferential links differs. D negates the initial antecedent and infers the negation of the final consequent, a different error from reversing the chain.