Describe the Flaw
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LSAT Logical Reasoning › Describe the Flaw
A city council report notes that neighborhoods with more trees have less crime. Therefore, planting more trees in high-crime areas will reduce crime rates.
fails to consider that other factors may contribute to both tree presence and crime reduction
concludes that trees are beneficial for all urban problems
relies on an untested assumption that trees affect crime rates
overlooks the possibility that low-crime areas are more likely to have trees
assumes that the presence of trees directly causes a reduction in crime
Explanation
The argument concludes that planting trees in high-crime areas will reduce crime rates based on the observation that neighborhoods with more trees have less crime. The reasoning commits the correlation-causation fallacy by assuming that the presence of trees directly causes crime reduction without considering alternative explanations for the observed correlation. Choice A correctly identifies this flaw by noting the assumption that trees directly cause crime reduction. Choice E describes reverse causation (a specific alternative explanation) but doesn't capture the fundamental error of assuming direct causation from correlation. When arguments jump from observational data to causal prescriptions, scrutinize whether causation has been properly established.
A teacher argues that a new reading app improves comprehension. In her class, students who used the app most frequently scored higher on the end-of-unit quiz. She infers that using the app caused the higher scores. Since higher quiz scores indicate better comprehension, she concludes that requiring all students to use the app daily will improve comprehension across the school.
Some students in the class used the reading app frequently.
Requiring all students to use the app daily will improve comprehension across the school.
Students who used the app most frequently scored higher on the end-of-unit quiz.
The argument assumes that higher quiz scores must have been caused by the app rather than by some other factor.
Because the app seems helpful, it will certainly raise every student’s score.
Explanation
The teacher concludes that requiring app use will improve comprehension school-wide based on correlational evidence between app usage frequency and quiz scores in her class. This reasoning confuses correlation with causation—higher-achieving students might naturally use the app more, making the app a symptom rather than a cause of better performance. The correct answer identifies the key evidence the argument relies on: that frequent app users scored higher on quizzes. Choice C correctly identifies the causation assumption flaw but represents the logical principle rather than the specific evidence gap. The argument's persuasiveness depends entirely on the correlation between app usage and performance, making this the crucial factual foundation. In flaw questions, distinguish between the evidence that supports the reasoning and the logical errors in interpreting that evidence.
Which of the following most accurately describes the error in reasoning?
Treats a necessary condition for success as if it were sufficient to guarantee success.
Presumes that two things similar in one respect are similar in all respects.
Attacks the grant committee members rather than their criteria.
Generalizes from a single case to an entire category.
Concludes a causal claim merely from the order in which events occur.
Explanation
The argument assumes that because thorough research is required for funding, having thorough research ensures funding. It does not depend on an analogy, a personal attack, or a hasty generalization. Nor does it infer causation from sequence.
The reasoning above is flawed for which of the following reasons?
It rejects a claim solely on the basis of its source.
It treats two alternatives as mutually exclusive when both could be true.
It confuses a comparison of percentages with a comparison of absolute numbers, ignoring differences in base rates.
It draws a universal generalization from a single, atypical instance.
It bases its conclusion on a sample that is unlikely to be representative of the group about which it draws a conclusion.
Explanation
A higher percentage increase does not show which city has more thefts without knowing the initial totals. The argument does not hinge on sampling, false dichotomy, or source-based dismissal. It also does not generalize from a single case.
The reasoning above is flawed for which of the following reasons?
It concludes that a policy is effective merely because it is popular.
It presumes that because two brands are different, one must be superior.
It generalizes from an unrepresentative sample to a broad population.
It equates a lack of contrary evidence with conclusive proof.
It overlooks the possibility that preferences can change over time, invalidating the result.
Explanation
Website commenters are a self-selected group that is unlikely to represent the broader population. Generalizing their preferences to all listeners is an unrepresentative sample flaw. The other options describe different errors (false dichotomy, appeal to popularity, appeal to ignorance, and temporal change) not made here.
The reasoning above is flawed for which of the following reasons?
It generalizes from a single department to the entire institution without basis.
It concludes that because something is possible, it is inevitable.
It presents a false dilemma by overlooking other plausible means of balancing the budget.
It infers causation from mere temporal sequence.
It presumes that a practice that is common is therefore acceptable.
Explanation
The argument treats raising prices or running a deficit as exhaustive while inadequately considering other options for balancing the budget. The other answer choices describe flaws not committed here.
The reasoning above is flawed for which of the following reasons?
It treats a percentage increase as if it established a greater absolute increase in number.
It restates its conclusion as a premise instead of providing support for it.
It shifts the meaning of a key term during the course of the argument.
It assumes that because one event follows another, the first caused the second.
It disputes a position by attacking the rival's motives rather than the evidence.
Explanation
A larger percentage increase does not guarantee a larger number of customers added if the initial bases differ. The argument does not infer causation from sequence, attack motives, or argue in a circle. There is no equivocation on a key term.
The reasoning above is flawed for which of the following reasons?
It infers that the whole will have a property merely because each part has that property in isolation.
It draws a causal conclusion without ruling out alternative causes.
It assumes that because the repertoire is the same, audience reactions will not change.
It fails to consider that a change in leadership could undermine performance.
It uses an unrepresentative sample to generalize about the entire orchestra.
Explanation
The argument assumes that improvements in individual sections guarantee perfect synchronization of the entire ensemble, ignoring interactions among sections. Properties of parts do not necessarily transfer to the whole. The other choices introduce issues (sampling, causation, leadership, audience reactions) not central to the reasoning.
The reasoning above is flawed for which of the following reasons?
It equivocates on the meaning of the term 'preference.'
It infers that what is true of a part must be true of the whole.
It presumes that a necessary condition is sufficient for the outcome in question.
It attacks the motives of those who hold a contrary view rather than addressing their arguments.
It bases a general conclusion about a population on an unrepresentative sample.
Explanation
Frequent patrons of one cafe are unlikely to represent the town as a whole. The other options describe different flaws—conditional confusion, composition, ad hominem, and equivocation—that are not committed here.
The reasoning above is flawed for which of the following reasons?
It discounts negative evidence solely because it is inconvenient.
It assumes that if a condition is sufficient for an outcome, then it is also necessary for that outcome.
It infers a trend from a single, atypical case.
It treats characteristics that are common among successful firms as if they were by themselves sufficient to ensure success.
It draws an analogy to investors' opinions without showing they are representative.
Explanation
The argument moves from 'most successful firms have traits T' to 'having T makes success likely,' illegitimately treating a typical feature of successes as sufficient. Many firms with T may still fail. The distractors describe other flaws (necessity/sufficiency reversal, weak analogy, hasty generalization, evidence dismissal) not shown here.