Logical Reasoning: Examples

Counselor: Those who believe that criticism should be gentle rather than harsh should consider the following: change requires a motive, and criticism that is unpleasant provides a motive. Since harsh criticism is unpleasant, harsh criticism provides a motive. Therefore, only harsh criticism will cause the person criticized to change. What is the flaw? A. Infers that something that is sufficient to provide a motive is necessary to provide a motive. B. Fails to address the possibility that in some cases the primary goal of criticism is something other than bringing about change in the person criticized. C. Takes for granted that everyone who is motivated to change will change. D. Confuses a motive for doing something with a motive for avoiding something. E. Takes the refutation of an argument to be sufficient to show that the argument's conclusion is false. - answer-FLAW Stimulus: P: Change -requires- motive Unpleasant criticism — motive IC: Harsh criticism — unpleasant criticism — motive MC: Change-requires- harsh criticism Assumption: motive -requires- harsh criticism A. Correct. The author assumes that since harsh criticism is sufficient for motive, it is also necessary for motive. This is a conditional logic flaw. A transit company's bus drivers are evaluated by supervisors riding with each driver. Drivers complain that this affects their performance, but because the supervisor's presence affects every driver's performance, those drivers performing best with a supervisor aboard will likely also be the best drivers under normal conditions. Which of the following is an assumption on which the argument depends? A. There is no effective way of evaluating the bus drivers' performance without having supervisors ride with them. B. The supervisors are excellent judges of a bus drivers' performance. C. For most bus drivers, the presence of a supervisor makes their performance slightly worse than it otherwise would be. D. The bus drivers are each affected roughly the same way and to the same extent by the presence of the supervisor. E. The bus drivers themselves are able to deliver accurate assessments of their driving performanc - answer-NECESSARY ASSUMPTION C is tempting. While this would suggest that bus drivers actually perform better in normal conditions, the conclusion is not that bus drivers will perform better than observed under supervision. Rather, the conclusion states that the best drivers under supervisor are also the best drivers under normal conditions. Additionally, it is not an assumption that the argument depends upon. D is correct. This assumption is necessary for the conclusion that the best drivers under supervision are also the best drivers under normal conditions. M, despite his generally poor appetite, thoroughly enjoyed the three meals he ate at the hotel, but, unfortunately, after each meal he became ill. The first time he ate an extra large pizza with peppers. The second time, he took full advantage of the all you can eat shrimp and peppers special. The third time, he had two giant meatballs with peppers. Since the only food all three meals had in common was peppers, M concluded that it was solely due to peppers that he became ill. M's reasoning is most vulnerable to which of the following criticisms? A. He draws his conclusions on the basis of too few meals that were consumed at the hotel. B. He posits a causal relationship without ascertaining that the presumed cause preceded the presumed effect. C. He allows his desire to continue dining at the hotel to bias his conclusion. D. He fails to establish that everyone at the hotel also became ill after eating peppers. E. - answer-FLAW Trick; not a causation flaw A. The argument does not do this. It does not extrapolate beyond the three meals. B. The argument does not do this. Becoming ill did not come before eating the peppers. E. Correct. It is given that M generally has a poor appetite. A museum director, in order to finance expensive new acquisitions, discretely sold some paintings by major artists. All of them were paintings that the directly privately considered inferior. Critics roundly condemned the sale, charging that the museum had lost first rate pieces, thereby violating its duty as a trustee of art for future generations. A few months after being sold by the museum, those paintings were resold, in an otherwise stagnant art market, at two or three tones the price paid to the museum. Clearly, the prices settled the issue, since they demonstrate the correctness of the critics' evaluation. The reasoning in the argument is vulnerable to the criticism that the argument does which of the following? A. It concludes that a certain opinion is correct on the grounds that it help by more people than hold the opposing view. B. It rejects the judgement of experts... C. It rejects a proven means of - answer-FLAW Trick; causation flaw, not a fact v opinion flaw Premise: Deemed inferior — sold cheaper Deemed superior — sold at a more expensive price Conclusion: Sold at more expensive price — proof that deemed superior A is tempting but does not occur. The conclusion does not determine that the art is superior because many people think so, but rather because it sold as a higher price. E is correct. There are numerous other factors that may have influenced why the paintings resold for the higher price (ex: influence of the critics' opinion) Advertisement: a leading economist has determined that among people who used computers at their place of employment last year, those who also owned portable computers earned 25% more on average than those who did not. It is obvious from this that owning a laptop computer led to a high paying job. Which of the following identifies a reasoning error in the argument? A. It attempts to support a sweeping generalization on the basis of information about only a small number of individuals. B. It's conclusion merely restates a claim made earlier in the argument. C. It concludes that one thing was caused by another although the evidence given is consistent with the first thing's having caused the second. D. It offers information as support for a conclusion when that information actually shows that the conclusion is false. E. It uncritically projects currently existing trends indefinitely into the future. - answer-FLAW Trick; causation flaw; potential relationship in the opposite direction D is correct. The evidence more strongly supports the conclusion that high include is responsible for owning a laptop computer. During this record breaking heat wave, air conditioning use has overloaded the region's electric power grid, resulting in frequent power blackouts throughout the region. For this reason, residents haven been asked to cut back voluntarily on air conditioning in their homes. But even if this request is heeded, blackouts will probably occur unless the heat wave abates. Which of the following, if true, most helps to resolve the apparent discrepancy in the information above? A. Air conditioning is not the only significant drain on the electrical system in the area. B. Most air conditioning in the region is used to cool businesses and factories. C. Most air-conditioning systems could be made more energy efficient by implementing simple design modifications. D. Residents of the region are not likely to reduce their air conditioner use voluntarily during particularly hot weather. E. The heat wave is expected to abate in th - answer-PARADOX Heat wave and AC — overload — blackout However, -AC among RESIDENTS — blackouts A is tempting. However, it is given that the heat wave and AC use are sufficient to cause blackouts. Other factors that cause blackouts should not disrupt this relationship. B describes the paradox. D is incorrect because the conclusion assumes that the request is satisfied. Political theorist: the chief foundations of all governments are the legal system and the police force; and as there cannot be a good legal system where the police are not paid well, it follows that where the police are paid well, there will be a good legal system. The reasoning in the argument is not sound because it fails to establish that A. Many governments with bad legal systems have poorly paid police forces. B. Bad governments with good legal systems must have poorly paid police forces. C. A well-paid police force cannot be effective without a good legal system. D. A well-paid police force is sufficient to guarantee a good legal system. E. Some bad governments have good legal systems. - answer-FLAW Conditional logic P: -police paid well — -legal system C: police paid well — legal system D A controversial program rewards prison inmates who behave particularly well in prison by giving them the chance to receive free cosmetic plastic surgery performed by medical students. The program is obviously morally questionable, both in its assumptions about what inmates might want and in its use of the prison population to train future surgeons. Putting these moral issues aside, however, the surgery clearly has a powerful effect rehabilitative effect, as is shown by the fact that, among recipients of the surgery, the proportion who are convicted of new crimes committed after release is only half that for the entire prison population as a whole. A flaw in the reasoning of the passage is that it A. Allows moral issues to be a consideration in presenting evidence about the matter of fact. B. Dismisses moral considerations on the grounds that only matters of fact are relevant. C. Labels the program as "controvers - answer-D is false. We are evaluating logic and reasoning, not what the author "should have done." E is correct. The sample only includes inmates with particularly good behavior. Cotrell, at best, is able to write magazine articles of average quality. The most compelling pieces of evidence for this are those few of the numerous articles submitted by Cotrell that are superior, since, Cotrell, who is incapable of writing an article that is better than average, must obviously have plagiarized the superior ones. The argument is most vulnerable to the criticism that A. It simply ignores the existence of potential counter evidence. B. It generalizes from atypical occurrences. C. It presupposes what it seeks to establish. D. It relies on the judgement of experts in a matter to which their expertise is irrelevant. E. It infers limits on ability from a few isolated lapses in performance. - answer-FLAW Circular reasoning; presupposes what it seeks to establish P: Cotrell is incapable of writing a better than average article IC: Cotrell must have plagiarized his few superior articles MC: Cotrell can write only low to average quality articles A does not ignore the presence of counter-evidence demonstrating superior performance. Rather, the author misinterprets. B is incorrect. There are "atypical occurrences" mentioned, but rather than generalize from these occurrences, the author attempts to prove the opposite of what they would imply C is correct. Council member: I recommend that the abandoned shoe factory be used as the municipal emergency shelter. Some council members assert that the courthouse would be a better shelter site, but they have provided no evidence of this. Thus, the shoe factory would be a better shelter site. A questionable technique used in the council member's argument is that of A. Asserting that a lack of evidence against a view is proof that the view is correct. B. Accepting a claim simply because advocates of an opposing claim have not adequately defended their view. - answer-FLAW A. is false because the council members never present evidence against the author's view. Rather, the council members present evidence--or lack thereof--for their own view B is correct. Principle: A police officer is eligible for a Mayor's Commendation if the officer has an exemplary record, but not otherwise; an officer eligible for the award who did something this year that exceeded what could be reasonable expected of a police officer should received the award if the act saved someone's life Conclusion: Officer Franklin should receive a Mayor's Commendation but Officer Penn should not From which of the following sets of facts can the conclusion be properly drawn using the principle? A. In saving a child from drowning this year, F and P both risked their lives beyond what could be reasonably expected of a police officer. F has an exemplary record but P does not. B. Both F and P have exemplary records, and each officer saved a child from drowning earlier this year. However, in doing so, F went beyond what could be reasonably expected; P did not ... - answer-SUFFICIENT ASSUMPTION P: Exemplary record -- eligible -Exemplary record -- -eligible C: Eligible + exceed + save life -- award A. Correct. Satisfies all conditions. B. Incorrect. Eligibility is both sufficient and necessary. In A, P lacks eligibility, so he will NOT receive the award. Furthermore, in B, P did not go beyond expectations when saving the child's life, but he may have gone beyond expectations during other acts. Thus, a lack of exceeding expectations is not sufficient to guarantee that P does NOT receive the award. Physician: the rise in blood pressure that commonly accompanies aging often results from a calcium deficiency. The deficiency is frequently caused by a deficiency in the active form of vitamin D, needed in order for the body to absorb calcium. Since calcium in one glass of milk per day can easily make up for any underlying calcium deficiency, some older people can lower their blood pressure by drinking milk. The physician's conclusion is properly drawn if which of the following is assumed? A. There is in milk, in a form that older people can generally utilize, enough of the active form of vitamin D and any other substances needed in order for the body to absorb the calcium in that milk. B. Milk does not contain any substance that is likely to increase BP in older people. C. Older people's drinking one glass of milk per day does not contribute to a deficiency in the active form of vitamin D needed in order for th - answer-SUFFICIENT ASSUMPTION Make sure to match the argument in strength. The stimulus uses language such as "often" and "some." P1: decrease in Vitamin D → decrease in C → increase in BP P2: Milk → increase in C C: Milk → decrease in BP Assumption: Milk → increase in Vitamin D → increase in C → decrease in BP *These are are not conditionals but rather correlated relationships A. Fills the gap between milk and vitamin D. Milk — increase in vitamin D — increase in C D. Decrease in vitamin D — decrease in C. This was already stated in the premise. It also uses extreme language that does not correspond with the stimulus. Incorrect. A recent poll showed that almost half of the city's residents believe that Major Walker is guilty of ethics violations. Surprisingly, however, 52% of those surveyed judged Walker's performance as mayor to be good or excellent, which is no lower than it was before anyone accused him of ethics violations. Which of the following, if true, most helps to explain the surprising fact stated above? A. Almost all of the people who believed that Walker is guilty of ethics had thought, even before he was accused of those violations. B. In the time since Walker was accused of ethics violations, there has been an increase in the percentage of city residents who judge the performance of Walker's opponents to be good or excellent. C. About a fifth of those polled did not know that Walker had been accused of ethics violations. D. Walker is currently up for re-election, and anti corruption groups in the city have expressed sup - answer-FLAW A proposes that the mayor's performance is poor and unethical are correlated. This is an explanation for the apparent discrepancy. This is correct. Loggerhead turtles live and breed in distinct groups, of which some are in the Pacific Ocean and some are in the Atlantic. New evidence suggests that juvenile Pacific loggerheads that feed near the Baja peninsula hatch in Japanese waters 10,000 kilo away. 95% of the DNA samples taken from the Baja turtles match those taken from the turtles at the Japanese nesting sites. Which one of the following, if true, most seriously weakens the reasoning above?