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LSAT Logical Reasoning study materials
LSAT Logical Reasoning study resources

LSAT Logical Reasoning practice questions

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Question 1Logical Reasoning

A critic argues: 'Every novel in the library that was published before 1950 is bound in cloth. Therefore, some novels bound in cloth were published before 1950.' Assuming the library contains at least one pre-1950 novel, the critic's reasoning is best described as which of the following?

  1. Invalid, because it assumes that no post-1950 novel is bound in cloth Correct answer.
  2. Valid, because it merely restates the premise in different words
  3. Invalid, because it illicitly converts a universal statement into an existential one
  4. Valid, because the conclusion follows from the premise by universal instantiation

Explanation

The premise is universal: all pre-1950 novels are cloth-bound. The conclusion asserts that at least one such novel exists and is cloth-bound, which requires an existential assumption the premise does not supply. Without a guaranteed instance, the inference is an illicit conversion of an 'all' claim into a 'some' claim.

Question 2Logical Reasoning

An editorial states: 'If the city raises parking fees, downtown merchants will lose customers. Downtown merchants have not lost customers. Therefore, the city did not raise parking fees.' This argument is an instance of which valid form?

  1. Modus tollens Correct answer.
  2. Denying the antecedent
  3. Modus ponens
  4. Affirming the consequent

Explanation

The argument takes the form 'If P then Q; not Q; therefore not P,' which is modus tollens and is deductively valid. Affirming the consequent and denying the antecedent are the two classic formal fallacies and do not match this structure.

Question 3Logical Reasoning

A reviewer claims: 'The new policy is either ineffective or expensive. We have established that it is not ineffective. So it must be expensive.' Which feature makes this disjunctive argument valid?

  1. The argument assumes that both disjuncts can be true simultaneously
  2. The argument relies on an unstated conditional connecting cost to effectiveness
  3. The conclusion is a restatement of the first premise
  4. The disjunction is treated as exclusive, so ruling out one disjunct forces the other Correct answer.

Explanation

The argument uses disjunctive syllogism: from 'P or Q' and 'not P,' infer Q. This inference is valid because at least one disjunct must hold, so eliminating one leaves the other regardless of whether the disjunction is exclusive.

Question 4Logical Reasoning

A study finds that students who eat breakfast score higher on morning exams. A columnist concludes that eating breakfast causes higher exam scores. Which consideration most weakens the columnist's causal claim?

  1. Breakfast foods vary widely in nutritional content across households
  2. Some students skip breakfast on weekends as well as exam days
  3. Students who regularly eat breakfast also tend to sleep more hours and study more consistently Correct answer.
  4. The study measured scores on only one morning exam

Explanation

The columnist infers causation from a correlation. If breakfast-eaters also differ in sleep and study habits, those factors could explain the higher scores, so the correlation does not isolate breakfast as the cause. This is the classic alternative-explanation challenge to a causal inference.

Question 5Logical Reasoning

A witness testifies: 'The intruder was either tall or wearing a hat. I am certain the intruder was not wearing a hat.' If the witness's statements are both true, which conclusion follows by valid inference?

  1. The intruder was tall and wearing a hat
  2. Nothing follows about the intruder's height
  3. The intruder was tall Correct answer.
  4. The intruder was neither tall nor wearing a hat

Explanation

From 'tall or wearing a hat' and 'not wearing a hat,' disjunctive syllogism yields that the intruder was tall. The inference is valid because at least one disjunct must be true and the second has been eliminated.

Question 6Logical Reasoning

An argument concludes: 'Therefore, the museum must be closed on Mondays.' Which of the following, if assumed, would most directly help the argument reach that conclusion?

  1. The museum's website lists holiday hours separately from regular hours
  2. Every museum that closes on Mondays does so for maintenance
  3. Visitors often prefer to attend museums on weekends
  4. The museum is closed on whatever day its staff training occurs, and staff training occurs on Mondays Correct answer.

Explanation

A sufficient assumption supplies the missing link between the evidence and the conclusion. The option connecting staff training to closure, plus the fact that training occurs on Mondays, directly entails the conclusion. The other options concern unrelated scheduling or visitor preferences.

Question 7Logical Reasoning

A politician says: 'My opponent voted against the bill, so my opponent does not care about children's health.' The reasoning is flawed primarily because it:

  1. Relies on a sample that is too small to support any generalization
  2. Treats opposition to a particular bill as proof of indifference to the bill's stated goal Correct answer.
  3. Assumes without justification that the bill would have passed
  4. Uses a term in two different senses within the same argument

Explanation

The speaker infers a motive (indifference to children's health) from a single behavioral fact (voting against a bill). Opposing one bill is compatible with caring about its goal, since one may object to the bill's means or details. This is a false inference about motives from limited evidence.

Question 8Logical Reasoning

A researcher notes: 'All participants who received the supplement improved. Therefore, the supplement is effective for everyone.' Which criticism of the conclusion is most accurate?

  1. It assumes the conclusion it sets out to prove, making it circular
  2. It commits the fallacy of equivocation on 'improved'
  3. It generalizes from a restricted group to everyone without justification Correct answer.
  4. It confuses a necessary condition with a sufficient condition

Explanation

The evidence concerns only the participants in the study, yet the conclusion extends the claim to everyone. That is an overgeneralization, since the sample may not represent the broader population. The other criticisms describe flaws not present in the stated reasoning.

Question 9Logical Reasoning

A company memo argues: 'Our sales rose after we redesigned the logo. The redesign therefore caused the increase.' Which additional fact, if true, would most strengthen this argument?

  1. Competitors also redesigned their logos during the same period
  2. The logo redesign was completed several months before the sales increase
  3. The company's sales had been declining for several years before the redesign
  4. No other marketing, pricing, or product changes occurred during the period in question Correct answer.

Explanation

Strengthening a causal claim often means ruling out alternative explanations. If no other relevant changes occurred, the logo redesign is more plausibly the cause of the sales increase. The other options either introduce confounds or fail to address competing causes.

Question 10Logical Reasoning

A city council member argues: 'We must either build the new bridge or accept worsening traffic. We cannot accept worsening traffic. Therefore, we must build the new bridge.' The argument's reasoning depends on which assumption?

  1. Building the bridge will fully eliminate traffic congestion
  2. Worsening traffic is more costly than building the bridge
  3. The two options presented are the only relevant alternatives Correct answer.
  4. The council has the authority to fund the bridge

Explanation

The argument is a disjunctive syllogism, which is valid only if the disjunction genuinely exhausts the alternatives. If a third option exists, eliminating one disjunct does not force the other. Thus the argument presupposes that the two options are exhaustive.

Question 11Logical Reasoning

A critic writes: 'Anyone who understands the novel must have read the final chapter. My student has not read the final chapter. So my student does not understand the novel.' Which statement best evaluates this argument?

  1. It is valid, since understanding a novel always requires reading all of it
  2. It is invalid, because it assumes the student read the earlier chapters
  3. It is valid, since it correctly applies modus tollens to a conditional claim Correct answer.
  4. It is invalid, because it treats a necessary condition as if it were sufficient

Explanation

The premise says understanding requires reading the final chapter, giving 'If understand, then read final chapter.' With 'not read final chapter,' modus tollens yields 'not understand,' so the argument is valid. The remaining options misdescribe either the form or the content of the reasoning.

Question 12Logical Reasoning

A journalist reports: 'Three of the five witnesses said the light was red. So the light was probably red.' Which additional information would most undermine the journalist's inference?

  1. The three witnesses who said red were together and discussed the event before testifying Correct answer.
  2. The intersection had recently installed new traffic signals
  3. The other two witnesses disagreed with each other about the color
  4. The witnesses were all standing at different corners of the intersection

Explanation

The inference treats the three agreeing witnesses as independent evidence. If they conferred before testifying, their agreement may reflect shared influence rather than independent observation, weakening the support for the conclusion. Independence is what gives multiple reports their combined weight.

Question 13Logical Reasoning

A policy analyst argues: 'Countries with higher literacy rates have higher average incomes. Therefore, raising literacy rates will raise average incomes.' The analyst's reasoning is most vulnerable to which objection?

  1. Average income is an imperfect measure of national wealth
  2. Some high-income countries have low literacy rates
  3. Literacy rates are difficult to measure accurately across countries
  4. The correlation may result from a third factor, such as industrialization, that raises both literacy and income Correct answer.

Explanation

The analyst moves from a correlation to a causal prescription. If a third factor such as industrialization drives both literacy and income, then raising literacy alone would not necessarily raise income. This common-cause challenge targets the causal leap directly.

Question 14Logical Reasoning

A defense attorney argues: 'The prosecution's case relies on a single eyewitness. Eyewitness testimony is sometimes mistaken. Therefore, the defendant is innocent.' Which description best captures the flaw?

  1. It attacks the character of the prosecution rather than its evidence
  2. It treats the possibility that the testimony is mistaken as proof that it is mistaken Correct answer.
  3. It draws a conclusion about the entire case from one piece of evidence
  4. It assumes that all eyewitnesses are equally reliable

Explanation

The argument notes that eyewitness error is possible and then concludes that the defendant is innocent, which requires the testimony to be actually mistaken. Possibility is being converted into certainty. The other options describe flaws not present in the stated reasoning.

Question 15Logical Reasoning

A historian claims: 'The treaty was signed only after the famine ended. Since the famine ended in 1847, the treaty must have been signed in 1847.' The historian's reasoning is flawed because it:

  1. Assumes that treaties are always signed in the same year a crisis ends
  2. Relies on an unreliable source for the date of the famine's end
  3. Confuses a condition that is necessary for signing with a condition that determines the date Correct answer.
  4. Overlooks the possibility that the treaty was never signed

Explanation

The claim 'signed only after the famine ended' makes the famine's end a necessary condition, not a sufficient one. Many events could occur after 1847, so the treaty could have been signed later. The error is treating a necessary condition as though it fixed the exact date.

Question 16Logical Reasoning

A nutritionist argues: 'People who take vitamin supplements visit doctors less often. Thus, taking supplements makes people healthier.' Which finding, if true, would most weaken this argument?

  1. Doctor visits are an imperfect measure of health
  2. Some people take supplements only when they feel ill
  3. Vitamin supplements are available without a prescription
  4. People who take supplements tend to be more health-conscious and exercise regularly Correct answer.

Explanation

If supplement users also exercise and are generally health-conscious, those habits could explain their fewer doctor visits, leaving no demonstrated effect of supplements. This introduces a plausible alternative cause, which undermines the causal conclusion.

Question 17Logical Reasoning

A mayor argues: 'If we expand public transit, then congestion will decrease. Congestion has decreased. Therefore, we expanded public transit.' The mayor's argument commits which error?

  1. Begging the question
  2. Denying the antecedent
  3. Affirming the consequent Correct answer.
  4. Equivocation

Explanation

The form is 'If P then Q; Q; therefore P,' which affirms the consequent and is invalid. A decrease in congestion could have other causes, such as a recession or new road pricing. The argument reverses the conditional without warrant.

Question 18Logical Reasoning

A reviewer argues: 'This restaurant must be excellent because it is always crowded.' Which assumption is required for the reviewer's conclusion to follow?

  1. Some excellent restaurants are not crowded
  2. A restaurant that is always crowded is likely to be excellent Correct answer.
  3. Crowded restaurants are generally more expensive than uncrowded ones
  4. The restaurant's popularity has increased over time

Explanation

The argument treats popularity as evidence of quality, so it needs the bridge that being consistently crowded tends to indicate excellence. Without that link, the premise about crowds does not support the conclusion. The other options either weaken the argument or are irrelevant to it.

Question 19Logical Reasoning

A scientist reports: 'In our sample of 40 volunteers, those who slept more than seven hours performed better on a memory test. We conclude that sleep improves memory in the general population.' Which feature of the study most limits this conclusion?

  1. The memory test was administered in the morning
  2. Sleep duration was self-reported rather than measured
  3. The study did not measure other cognitive abilities
  4. The sample was small and may not represent the general population Correct answer.

Explanation

The conclusion extends a finding from 40 volunteers to the general population, and a small sample may not be representative. This is the central limit on generalizing the result. Other features may affect reliability but do not directly block the population-wide inference.

Question 20Logical Reasoning

A commentator argues: 'Either the senator knew about the funding or she was negligent. She was not negligent. Therefore, she knew about the funding.' The argument is valid only if which of the following holds?

  1. The senator has denied knowing about the funding
  2. The two alternatives exhaust the relevant possibilities Correct answer.
  3. Negligence is a more serious charge than knowledge
  4. Negligence and knowledge cannot both occur in the same person

Explanation

The argument relies on disjunctive syllogism, which is valid when the disjunction covers all possibilities. If a third option exists, such as being misinformed through no fault, excluding negligence would not force knowledge. Thus exhaustiveness is the needed assumption.

Question 21Logical Reasoning

An economist argues: 'When tariffs were raised, domestic production rose. When tariffs were lowered, domestic production fell. Therefore, tariffs cause domestic production to rise.' Which consideration most seriously challenges this reasoning?

  1. Domestic production is difficult to measure precisely
  2. Some industries benefited from tariffs while others did not
  3. Tariffs were changed by legislators rather than by economists
  4. Both tariff changes coincided with broader economic cycles that independently affect production Correct answer.

Explanation

The economist infers causation from a pattern of co-variation. If both changes coincided with broader economic cycles, those cycles could explain the production shifts, so the correlation does not isolate tariffs as the cause. A confound affecting both periods undermines the causal inference.

Question 22Logical Reasoning

A philosopher argues: 'Every action that is morally required is also rationally required. Some actions are rationally required but not morally required. Therefore, not every rationally required action is morally required.' Which statement about this argument is accurate?

  1. It is invalid because it assumes that moral requirements are rational requirements
  2. It is invalid because it equivocates on 'required'
  3. It is valid, since the second premise directly contradicts the conclusion's negation Correct answer.
  4. It is invalid because it generalizes from a single case

Explanation

The second premise asserts that at least one rationally required action is not morally required, which is exactly what the conclusion states. The first premise is not even needed. The argument is therefore valid, and the remaining options misidentify its structure.

Question 23Logical Reasoning

A researcher argues: 'Patients who received the experimental drug recovered faster than those who did not. Because assignment to the drug was based on the severity of illness, with milder cases receiving the drug, the drug cannot be credited with the faster recovery.' Which statement best evaluates this argument?

  1. It is flawed, since it assumes that severity of illness cannot be measured
  2. It is flawed, since faster recovery is always caused by the drug under study
  3. It is sound, since severity of illness is a plausible alternative explanation for the difference in recovery Correct answer.
  4. It is sound, since it establishes that the drug has no effect on any patient

Explanation

Because milder cases were assigned to the drug, the severity difference is a confound that could fully explain the faster recovery. The argument correctly identifies this alternative explanation, so its conclusion that the drug cannot be credited is well supported. The other options either overstate the conclusion or misidentify the reasoning.

Question 24Logical Reasoning

A theorist argues: 'If determinism is true, then every choice is caused by prior events. If every choice is caused by prior events, then no one is morally responsible. Some people are morally responsible. Therefore, determinism is false.' Which best describes the logical structure of this argument?

  1. A chain of conditionals combined with modus tollens Correct answer.
  2. A disjunctive syllogism combined with modus ponens
  3. An argument that commits the fallacy of affirming the consequent
  4. An argument that begs the question by assuming free will

Explanation

The argument links two conditionals to derive 'If determinism is true, then no one is morally responsible.' Combined with the premise that some people are morally responsible, it uses modus tollens to conclude that determinism is false. The structure is a hypothetical chain plus denial of the consequent.

Question 25Logical Reasoning

A columnist argues: 'The new museum has attracted large crowds. Since large crowds indicate public interest, and public interest justifies public funding, the museum deserves public funding.' Which criticism most directly targets the reasoning?

  1. It relies on the opinions of visitors rather than experts
  2. It confuses the cost of the museum with its cultural value
  3. It assumes that large crowds always reflect genuine interest rather than free promotional events Correct answer.
  4. It fails to consider whether other museums also attract large crowds

Explanation

The argument depends on crowds being a reliable sign of public interest. If the crowds were drawn by free promotional events, the attendance would not establish genuine interest, breaking the chain to the funding conclusion. The other criticisms raise issues that do not directly attack the inferential link.

Question 26Logical Reasoning

A gallery owner argues: "Our attendance doubled the month we began offering free admission. Clearly, free admission caused the increase in attendance." The reasoning is most vulnerable to criticism because it

  1. relies on the testimony of people whose reliability is never established
  2. confuses a necessary condition of increased attendance with a sufficient one
  3. assumes that attendance would not have risen for some other reason during that month Correct answer.
  4. draws a conclusion about a whole population from a single case

Explanation

The argument treats a temporal coincidence as proof of causation, which requires ruling out alternative explanations for the same rise. If some other factor (a new exhibition, a holiday, a rival closing) produced the increase, the causal claim collapses.

Question 27Logical Reasoning

A school board member says: "If we adopt the longer school day, test scores will improve. Test scores did not improve. Therefore, we did not adopt the longer school day." This reasoning is valid only if which of the following is assumed?

  1. Adopting the longer school day guarantees improved test scores. Correct answer.
  2. The longer school day would be popular with parents.
  3. Adopting the longer day is the only way to improve test scores.
  4. Test scores are the most important measure of school quality.

Explanation

The argument uses the pattern: if P then Q; not Q; therefore not P. This modus tollens form is valid only when the conditional premise genuinely guarantees Q whenever P holds. The stated premise already supplies that guarantee, so the argument's validity hinges on reading the conditional as a strict guarantee rather than a tendency.

Question 28Logical Reasoning

A food critic writes: "Every dish at this restaurant that I have sampled has been excellent. Therefore, every dish on the menu is excellent." The critic's reasoning is flawed because it

  1. generalizes from a sample that may not represent the whole menu Correct answer.
  2. treats a claim about individual dishes as if it were about the restaurant
  3. uses the word 'excellent' in two different senses
  4. assumes without justification that the chef is skilled

Explanation

The critic moves from a subset of sampled dishes to the entire menu, which is legitimate only if the sample is representative. Dishes not sampled may differ systematically, so the conclusion is not supported.

Question 29Logical Reasoning

A tenant argues: "My landlord must fix the heating, because the lease says the landlord must keep the unit habitable, and a unit without heat is not habitable." Which of the following best describes the structure of this argument?

  1. It draws an analogy between heating and other repairs.
  2. It attacks the character of the landlord rather than the lease.
  3. It infers a cause from a correlation between two events.
  4. It applies a general rule to a specific case to reach a conclusion. Correct answer.

Explanation

The tenant states a general rule (habitability must be maintained), supplies a factual premise (no heat means not habitable), and concludes that a particular obligation applies. That is deductive application of a rule to a case.

Question 30Logical Reasoning

A witness testifies: "I saw the defendant leave the building at 9 p.m." A detective reasons: "If the witness is accurate, the defendant was in the building at 9 p.m. But the defendant was not in the building at 9 p.m. So the witness is not accurate." The detective's reasoning is

  1. invalid, because the witness might have been mistaken about the building
  2. weak, because it relies on a single conditional premise
  3. circular, because it assumes what it sets out to prove
  4. valid, because it denies the consequent of a conditional Correct answer.

Explanation

The detective reasons: if accurate, then present; not present; therefore not accurate. This is denying the consequent, a valid form when the conditional is read as a strict implication. The conclusion follows necessarily from the two premises.

Question 31Logical Reasoning

An editorial states: "Either the city raises parking fees or downtown traffic will worsen. The city will not raise parking fees. Therefore, downtown traffic will worsen." The editorial's conclusion follows logically if which of the following is true?

  1. Downtown traffic has worsened in each of the past three years.
  2. Raising parking fees is unpopular with most downtown merchants.
  3. The city has other ways to reduce downtown traffic.
  4. Raising parking fees would reduce downtown traffic. Correct answer.

Explanation

The argument has the form: P or Q; not P; therefore Q. This disjunctive syllogism is valid only if the two options are genuinely exclusive and the first is truly the alternative to the second. If raising fees would not reduce traffic, the 'either/or' premise is unsupported and the inference fails.

Question 32Logical Reasoning

A reviewer argues: "This novel is poorly written because its author was unknown before publication." The reviewer's reasoning is flawed because it

  1. assumes that unknown authors always write poorly Correct answer.
  2. rejects a claim on the basis of the person who made it rather than the claim's merits
  3. treats a claim about a novel's quality as a claim about its sales
  4. relies on a sample of readers that is too small

Explanation

The reviewer infers poor quality from the author's prior obscurity, which is relevant only if obscurity reliably predicts poor writing. That assumption is unwarranted, so the conclusion about the novel does not follow.

Question 33Logical Reasoning

A manager notes: "All employees who completed the safety course passed the inspection. Therefore, completing the course is sufficient for passing the inspection." Which of the following, if true, would most weaken this conclusion?

  1. Several employees who completed the course also had prior safety training. Correct answer.
  2. The inspection standards were revised after the course ended.
  3. Some employees who passed the inspection had not completed the course.
  4. The course was offered only to employees with at least one year of service.

Explanation

To show the course is not sufficient, one must show a case where the course was completed but the inspection was still failed, or that something else explains the passes. Option 2 suggests the passing employees had an additional factor, undermining the claim that the course alone suffices.

Question 34Logical Reasoning

A commentator argues: "The senator's proposal would reduce the deficit, because every economist who has reviewed it says so." Which of the following, if true, most seriously undermines the argument?

  1. The proposal is lengthy and technically complex.
  2. The senator has proposed deficit-reduction measures before.
  3. The economists who reviewed the proposal were selected by the senator's staff. Correct answer.
  4. Some economists disagree about how the deficit should be measured.

Explanation

The argument's force depends on the reviewers being an unbiased source of expert judgment. If the senator's staff chose them, the sample may be skewed toward favorable views, so the appeal to expert consensus is weakened.

Question 35Logical Reasoning

A study finds that students who eat breakfast score higher on exams than students who skip it. The researchers conclude that eating breakfast raises exam scores. Which of the following, if true, most weakens the conclusion?

  1. Breakfast foods vary widely in nutritional content.
  2. Students who eat breakfast tend to come from households that also provide tutoring and quiet study space. Correct answer.
  3. Some students who eat breakfast still score below average.
  4. The study measured scores on a single exam.

Explanation

The conclusion is causal, but the evidence is only a correlation. If breakfast eaters also enjoy other advantages that raise scores, those advantages could explain the difference, leaving no need to posit breakfast as the cause.

Question 36Logical Reasoning

A novelist says: "Anyone who has read my latest book knows the ending is ambiguous. My editor has not read the latest book. Therefore, my editor does not know the ending is ambiguous." The novelist's reasoning is flawed because it

  1. assumes that only reading the book can produce knowledge of the ending Correct answer.
  2. confuses the editor's opinion with the truth about the ending
  3. treats the editor's ignorance as evidence about the book's quality
  4. relies on the editor's professional expertise in an irrelevant way

Explanation

The first premise says reading the book is sufficient for knowing the ending, but the argument treats it as necessary. The editor might have learned the ending from the author or a draft, so the conclusion does not follow.

Question 37Logical Reasoning

A council member argues: "We should either build the new stadium or lose our professional team. Losing the team would be a disaster. So we should build the stadium." The argument depends on assuming that

  1. professional sports teams always benefit a city's economy
  2. no third option, such as renegotiating the lease, would keep the team Correct answer.
  3. the stadium would pay for itself within a decade
  4. residents overwhelmingly support building the stadium

Explanation

The argument presents only two alternatives and eliminates one, concluding the other. That move is valid only if the alternatives are exhaustive. If renegotiating the lease or another strategy could retain the team, the disjunction is false and the conclusion unsupported.

Question 38Logical Reasoning

A historian writes: "The famine ended shortly after the new grain policy was introduced, so the policy ended the famine." Which of the following, if true, most undermines the historian's reasoning?

  1. The famine also ended in neighboring regions that never adopted the policy. Correct answer.
  2. The grain policy was controversial among landowners.
  3. The policy was repealed several years later.
  4. Records from the period are incomplete.

Explanation

If the famine ended even where the policy was absent, the policy cannot be the explanation for its end. This comparison supplies strong evidence against the causal claim.

Question 39Logical Reasoning

A philosopher argues: "Every action that is morally required is also rationally required. Some actions are rationally required but not morally required. Therefore, some morally required actions are not rationally required." This argument is

  1. invalid, because it assumes that morality and rationality are identical
  2. valid, because the second premise supplies a counterexample
  3. invalid, because its conclusion contradicts the first premise Correct answer.
  4. valid, because it correctly applies the first premise to a specific case

Explanation

The first premise states that all morally required actions are rationally required. The conclusion asserts that some morally required actions are not rationally required, which directly contradicts that premise. An argument whose premises cannot all be true alongside its conclusion is invalid.

Question 40Logical Reasoning

A hospital reports: "Patients given the new drug recovered faster than patients given the old drug. Therefore, the new drug is more effective." Which of the following, if true, most weakens the conclusion?

  1. The new drug costs more to produce than the old drug.
  2. Patients given the new drug were, on average, significantly younger and healthier than those given the old drug. Correct answer.
  3. The new drug has been available for only two years.
  4. Some patients given the old drug recovered quickly.

Explanation

The comparison is only meaningful if the groups were otherwise similar. If the new-drug group started out younger and healthier, their faster recovery may reflect that advantage rather than the drug, so the causal conclusion is undermined.

Question 41Logical Reasoning

A columnist writes: "Most readers of the newspaper favor the new tax. Therefore, most residents of the city favor the new tax." The columnist's reasoning would be strengthened most by showing that

  1. the newspaper's editorial board endorses the new tax
  2. most residents have heard of the new tax
  3. the new tax has been debated for several months
  4. newspaper readers are roughly representative of the city's residents Correct answer.

Explanation

The argument generalizes from a subgroup (readers) to the whole population (residents). That inference is sound only if the subgroup resembles the population in the relevant respect, so evidence of representativeness strengthens it.

Question 42Logical Reasoning

A teacher argues: "If a student studies every day, that student will pass. Maria passed. Therefore, Maria studied every day." The teacher's reasoning is flawed because it

  1. assumes that Maria is a typical student
  2. concludes that Maria will pass in future courses
  3. treats a condition sufficient for passing as though it were necessary Correct answer.
  4. uses the word 'pass' ambiguously

Explanation

The argument affirms the consequent: if studying then passing; passing; therefore studying. This is invalid because passing may have other causes. The teacher wrongly treats daily study as required for passing when the premise presents it only as sufficient.

Question 43Logical Reasoning

An analyst argues: "Countries with higher literacy rates have higher average incomes. Therefore, raising literacy will raise average incomes." Which of the following, if true, most weakens the argument?

  1. Some countries with high literacy have low average incomes.
  2. Literacy rates are measured differently across countries.
  3. Average income is one of several measures of national well-being.
  4. Higher average incomes allow families to keep children in school longer, which raises literacy. Correct answer.

Explanation

The argument moves from correlation to a causal claim in one direction. If the causal arrow runs the other way, higher incomes producing higher literacy, then raising literacy would not necessarily raise incomes, and the inference fails.

Question 44Logical Reasoning

A witness says: "The defendant could not have committed the crime, because she was at a conference in another city that morning." Which of the following, if true, most strengthens the witness's claim?

  1. The crime occurred in the early afternoon.
  2. The conference was attended by several hundred people.
  3. The defendant has no prior criminal record.
  4. The defendant's attendance at the conference is confirmed by signed records and video. Correct answer.

Explanation

The witness's claim rests on the defendant being elsewhere at the relevant time. Independent, verifiable evidence of her presence at the conference strongly supports that alibi, making the claim more credible.

Question 45Logical Reasoning

A critic argues: "This film must be a masterpiece, since it won three major awards." Which of the following is an assumption required by the argument?

  1. Most filmgoers have seen the film.
  2. The film's director has won awards before.
  3. Awards are generally a reliable indicator of a film's artistic merit. Correct answer.
  4. The awards were announced in the same year.

Explanation

The argument infers artistic merit from award wins, which works only if awards reliably track merit. Without that bridge, the awards do not support the conclusion.

Question 46Logical Reasoning

A researcher argues: "In our sample, people who exercised daily reported better moods than those who did not. Because participants chose their own exercise habits, we cannot conclude that exercise improves mood." The researcher's point is that the study

  1. lacks random assignment, so a third factor may explain both exercise and mood Correct answer.
  2. measured mood with an unreliable self-report instrument
  3. failed to define what counts as daily exercise
  4. used too small a sample to detect any effect

Explanation

When participants self-select into groups, the groups may differ in other ways that affect the outcome. The researcher's caution is that without random assignment, some common cause could drive both exercise and mood, blocking a causal conclusion.

Question 47Logical Reasoning

A theorist argues: "If determinism is true, every choice is caused by prior events. If every choice is caused by prior events, no one is morally responsible. Some people are morally responsible. Therefore, determinism is false." The theorist's argument is

  1. valid, because it derives the negation of determinism from a chain of conditionals and a denial of the consequent Correct answer.
  2. valid, because it establishes that prior events never cause choices
  3. invalid, because it treats moral responsibility as a matter of opinion
  4. invalid, because it assumes that determinism and responsibility are unrelated

Explanation

The argument chains two conditionals to get: if determinism, then no one is responsible. It then denies the consequent (some people are responsible) to conclude that determinism is false. This is a valid hypothetical syllogism combined with modus tollens.

Question 48Logical Reasoning

A columnist argues: "The new museum has drawn large crowds, and large crowds indicate genuine public interest. Since public interest justifies public funding, the museum deserves public funding." Which of the following, if true, most weakens the argument?

  1. Many visitors came on free-admission days sponsored by a corporation, not out of interest in the exhibits. Correct answer.
  2. The museum received some private donations.
  3. The museum is located near a popular park.
  4. Other museums in the city have also attracted crowds.

Explanation

The argument depends on crowds reflecting genuine interest. If many visitors were drawn by free admission rather than the exhibits, the key link between crowds and interest breaks, weakening the case for funding.

Question 49Logical Reasoning

A scientist reasons: "If the compound is present, the sample turns blue. The sample turned blue. Therefore, the compound is present." Which of the following, if true, most strengthens the conclusion?

  1. The compound has been detected in similar samples before.
  2. The sample was stored in a blue container.
  3. The test was performed by an experienced technician.
  4. No substance other than the compound turns the sample blue under these conditions. Correct answer.

Explanation

The inference is invalid as stated because other substances might also turn the sample blue. If no other substance can do so under these conditions, then the blue result uniquely indicates the compound, and the conclusion becomes well supported.

Question 50Logical Reasoning

A policy analyst argues: "The program reduced unemployment, because unemployment fell after the program began. To test this, we should compare regions that adopted the program with otherwise similar regions that did not." The analyst's proposal is best understood as

  1. a way of controlling for confounding factors by using a comparison group Correct answer.
  2. an appeal to authority rather than evidence
  3. an argument that correlation always establishes causation
  4. a rejection of the claim that the program had any effect

Explanation

Comparing treated regions with similar untreated ones helps isolate the program's effect from other changes occurring at the same time. This is the logic of a control group, which addresses confounding variables.