《批判性推理策略》PPT课件

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1、Strategy for Critical ReasoningProvided by : piyusht Aim Logic, not GrammarCritical Reasoning problems are among the trickiest question types youll come across in the GMAT.Thats because CR problems are logic-based.While an understanding of English grammar rules is essential, your major challenge wil

2、l be simply to learn how ETS expects you to approach the information within the sentences.For many, this is the most feared part of the test! Why do they fear it so?Because the world as we know it is not logical. By deconstructing a Critical Reasoning argument, you can more clearly see what it is th

3、ats missing.Deconstructing an argument helps you notice illogical connections. The tendency to make sense of what we read is natural and, for the GMAT, fatal.Fight your normal reading habits as you go through the questions in this lesson. With each CR question, youll be presented with an argument. D

4、ont try to break down the argument into its essential parts.Instead, reorder the information.Reorder the information; identifying the premises and conclusion inherent within each argument.For Critical Reasoning questions, you must be purely and consistently logical. You: Lets go see a movie.Me: I ha

5、ve only two dollars.Make sure youre not brining outside information into your reading of a Critical Reasoning problem.We pose arguments all the time.Often there is no logical connection between the information we present (our premises) and our conclusions.For exampleWhat is your conclusion? We cant

6、go to a movie.Because a movie costs more than two dollars.But why?But how do we know this? We dont!Dont assume information unless you see it in the argument! Me: I cant believe I saw Joe drinking a Coke.You: Why?Me: Because Joe works for Pepsi.Whats your conclusion?Joe prefers Coca Cola.Joe hates hi

7、s job.Joe is a spy for Pepsi.Be careful! What kinds of assumptions are you making to reach these conclusions? Heres another example On Thursday I wore a blue shirt.On Friday I had a headache.Therefore, my blue shirt gives me a headache.This is a dumbed-down version of a Critical Reasoning problem. I

8、ts easy to argue with my logic when I present my argument so simply.Be always suspicious of CR arguments. Fight with them. What could you say that would undermine my argument?Perhaps I was out all night last Thursday.Maybe I live next door to an airport. Any of these statements could severely underm

9、ine, or weaken, my argument. And what could you add that would completely destroy it? What do you make of this one? Theres no connection between the headache and the shirtOn Thursday I wore a blue shirt.On Friday I had a headache.My health is affected by the clothes I wear.Therefore, my blue shirt g

10、ives me a headache.This piece of information would completely destroy my argument.And the reverse, that there is a direct connection between the headache and the shirt, would completely fix it.Now take a look at my revised argument Youll never find an argument like this in a Critical Reasoning probl

11、em. Its too logical! Your task as you approach CR questions will be to break down an illogical argument into its stated premises and conclusion.If you can do this, youll be able to spot any trick that ETS test-makers throw at you.There are several different types of Critical Reasoning questions. Dif

12、ferentiating between them is difficult, and youll have to know the approach for each of them when you sit down to take the test.Critical Reasoning questions ask you to do several things, but central to them all is having an understanding of the basic structure of an argument. Key TermsArgumentCentra

13、l to every CR question is the argument. An argument is an ordered line of reasoning composed of premises, assumptions, and a conclusion. Understanding the elements of an argument is essential to performing well in this section.PremiseEach CR argument contains at least one premise. Premises are piece

14、s of information that provide evidence used to support the conclusion of the argument. For the purposes of Critical Reasoning arguments, premises are facts not subject to dispute. ConclusionThe conclusion is the endpoint of the line of reasoning of an argument. Think of it as the result of the argum

15、ent. The line of reasoning leading to a conclusion is often where errors in logic are made. Key TermsAssumptionAssumptions are unstated facts and logical connections in an argument. In order for the conclusion of an argument to be true, the assumptions upon which that argument is based must also be

16、true. The Approach Step 1: Read the question first.Step 2: Read the argument.Step 3: Paraphrase the argument using your own words.Step 4: Predict the answer.Step 5: Use the process of Error Identification to eliminate the wrong answers.The Approach Critical Reasoning questions test your ability to u

17、se basic logic to analyze and critique arguments made up of premises and conclusions. ETS test-makers write arguments that assume information which doesnt exist!A logical and consistent approach is the best way to avoid formulaic traps.Follow these steps each time you attack Critical Reasoning quest

18、ions. Its natural to read the question after the argument because thats how theyre presented on the page. This is done for a reason.Step 1: Read the question first.Reading the argument first is confusing.Read the question and determine what to look for within the answer choices.In general, youll be

19、looking for the answer choices that either strengthen or weaken the argument.Think of answer choices as additional premises. Adding any one answer choice to the argument will do one of three things:1. It will weaken the argument.2. It will strengthen the argument. 2. It will not affect the argument

20、at all (neutral).3. It has nothing to do with the argument (out of scope).Determine which of the eight kinds of Critical Reasoning questions youre facing before turning to the argument itself. Step 2: Read the argument.1. Identify each premise (each piece of information) that is being presented with

21、in the argument.2. Identify the arguments conclusion.3. Determine what assumptions are being made.Step 3: Paraphrase the argument using your own words.Critical Reasoning arguments are intentionally heavy, wordy and complex. Paraphrasing is a good way of understanding the sense an argument presented.

22、 Take the time, if necessary, and restate an argument, using words and situations that you can relate to.Note: This is the only step youre permitted to skip. While its necessary to understand the meaning of each argument (and paraphrasing is a good tool to help you do this), restating or paraphrasin

23、g an argument brings you unavoidably further away from the actual text. Step 4: Predict the answer.So, youve read the argument. You understand it. You can identify its premises and its conclusion. Now imagine additional premises (additional pieces of information) and what affect each would have on t

24、he argument overall.Brainstorm for a moment. Imagine which additional premise would best strengthen the argument. What one thing could you add that would completely fix it? Now imagine the opposite. How could you weaken the argument? How could you completely destroy it?This is perhaps the most impor

25、tant step in the process. Answer choices are intentionally misleading, and you can use your predictions as a measuring stick with which to compare the choices given to you by ETS. Think of answer choices as additional premises. As you read each choice, ask yourself, “How would this additional premis

26、e affect the strength or weakness of the arguments conclusion?”Categorize answer choices as one of the following:1. Strengthen2. Weaken2. Neutral3. Out of scopeUse the Process of Error Identification to get rid of any choices that do not affect the conclusion (neutral) or have nothing to do with the

27、 argument whatsoever (out of scope).Whether you eliminate strengthen or weaken answer choices depends on the question related with that argument. Try the following Critical Reasoning example, using five steps Step 5: Use the Process of Error Identification to eliminate the wrong answers. In years pa

28、st, professional baseball players lifted weights less but were also injured less often during games. Obviously, the more an athlete lifts weights, the higher the likelihood of injury.The conclusion above presupposes which of the following?(A) The increase in baseball injuries is due to a factor othe

29、r thanweightlifting.(B) The activities of baseball players represent those of athletesas a group.(C) Most baseball injuries today result from too much weight-lifting.(D) There is no proven correlation between how much athletes liftweights and how likely they are to be affected by injury.(E) Weightli

30、fting has always been common practice forprofessional athletes. First, read the question.The conclusion above presupposes which of the following?Premise #1: In years past, professional baseball players lifted weights less.Premise #2: But they were also injured less often during games. Conclusion: Ob

31、viously, the more an athlete lifts weights, the higher the likelihood of injury.This is whats called an assumption question. What specific piece of information is presupposed (assumed) in the preceding argument?Break it down to understand what the writer is really saying.Can you identify the premise

32、s and the conclusion?Restate or paraphrase the argument, if necessary. Stick as close to the actual text as possible. The correct answer is (B). Lets see how its done If necessary, paraphrase the argument. Put the events in a context you can understand, but stick as close to the actual text as possi

33、ble. Try changing the subjects without changing what they did.Keep trying until the GMAT argument makes sense to you. Then return to the actual argument!Now, think about some of the big assumptions that are being made.Ask yourself what you could add to fix the argument. What could you add to the arg

34、ument to completely destroy it!If it helps, imagine someone you cant stand. Think up a real or fictional know-it-all. Now come up with the one thing you could say to this person that would shut him up. What if I offered evidence that proved baseball injuries are definitely not a result of weightlift

35、ing? That might destroy the argument. And the contrary, that baseball injuries definitely are a result of weightlifting, might fix it.What other assumptions can you come up with? When youre ready, turn your attention to the answer choices.Use the Process of Error Identification to eliminate any answ

36、er choices that are neutral or out of scope. For this particular question, also eliminate any answer choices that weaken the argument.(A) The increase in baseball injuries is due to a factor other than weightlifting.(B) The activities of baseball players represent those of athletes as a group.(C) Mo

37、st baseball injuries today result from too much weightlifting.(D) There is no proven correlation between how much athletes lift weights and how likely they are to be affected by injury.(E) Weightlifting has always been common practice for professional athletes. (A) The increase in baseball injuries

38、is due to a factor other than weightlifting.(B) The activities of baseball players represent those of athletes as a group.(C) Most baseball injuries today result from too much weightlifting.(D) There is no proven correlation between how much athletes lift weights and how likely they are to be affect

39、ed by injury.(E) Weightlifting has always been common practice for professional athletes.Only answer choices (B) and (C) strengthen the argument.Of course, there are many different kinds of athletes. All athletes are not baseball players. The correct answer is (B).Be aware of vague and undefined cat

40、egories, such as “athletes.”Whats wrong with answer choice (C) ? The trigger word “most” is undefined. “Most” is a relative term, but we dont know what its relative to. WeakensWeakensNeutral In 1991, produce growers began using a new, inexpensive pesticide, provoking many objections that they would

41、damage both the environment and the produce they were growing. However, the fears have proven unfounded as, though 1996, produce prices had dropped and no ill effects had been reported.Which of the following, if true, would be the strongest objection to the argument above?(A) Consumption of the prod

42、uce declined from 1991 to 1993, butrose sharply from 1994 to 1996.(B) Several areas in which use of the pesticide was forbiddenhave also experienced a drop in produce prices.(C) The amount of produce grown in 1991 was larger than that of1996.(D) The time since the beginning of the use of the pestici

43、de has been too short to allow some of the predicted effects to occur.(E) Since 1992, new pesticides have been developed thatscientists agree are relatively risk-free. Try one more (D) is the only answer choice that weakens the argument.All the others, in fact, are out of scope!Make it personalIn 19

44、91, I started smoking cigarettes. My friends said it is unhealthy. In 2000, I am still Okay: Therefore; cigarettes are not unhealthy. Theres a fatal flaw to this logic. Look back and compare this rephrasing with the actual argument itself.Sorry, the correct answer is (D). (D) is the only answer choi

45、ce that weakens the argument.All the others, in fact, are out of scope!Make it personalIn 1991, I started smoking cigarettes. My friends said it is unhealthy. In 2000, I am still Okay: Therefore; cigarettes are not unhealthy. Theres a fatal flaw to this logic. Look back and compare this rephrasing w

46、ith the actual argument itself.Good job! Good luck!Practice, Practice, Practice!The best way to prepare for Critical Reasoning questions is to practice Critical Reasoning questions.Take your time as you go through the test questions in the next section.If have difficulties, dont worry. Critical Reas

47、oning is the most dreaded question type in the exam! Click on the Next Screen button to see a brief description of these eight Critical Reasoning question types.Critical Reasoning Question TypesThe GMAT is, if anything, predictable.There is a limited variety of questions youll be asked relating to a

48、 Critical Reasoning argument.There are, in fact, eight definitive types of Critical Reasoning questions. Each question type has its own traps and a specific strategy is required to ace each one of them. Critical Reasoning Question Types1. Draw a conclusion2. Assumption3. Strengthen4. Weaken5. Infere

49、nce6. Explain the (apparent) contradiction7. Complete the passage8. “Except” questions Fire! Click on the oval that corresponds with your choice. A scientist planted two groups of plants under identical conditions of light, temperature, humidity, and moisture. Every day he would play sound effects o

50、f thunderstorms to one of the groups of plants and sounds of city traffic for the other. The group to which he played thunderstorms all died within a few weeks, but the other group thrived during the experiment. He therefore concluded that the sound of city traffic is more effective for helping plan

51、ts grow than is the sound of thunderstorms.Which of the following, if true, would most seriously weaken the scientists conclusion?(A) The scientist put different varieties of plants in each group.(B) The light affecting the plants changed according to the time of day. (C) The plants in the group for

52、 which he played city traffic soundsdied several weeks after the experiment.(D) The plants were all purchased at the same time.(E) The plants in the group for which he played city traffic soundsrequired more water than the scientist actually gave them.Weigh each choice carefully before eliminating i

53、t. Youve got it! We know we have two groups of plants. Whats assumed is that both groups are the same!Try a harder oneIn response to years of increasing congestion at airport X, the government decided to redistribute landing slots. Henceforth, all international flights arriving from continent A woul

54、d be rerouted to nearby airport Y, all flights arriving from continent B would continue to land at airport X. Several airlines opposed this measure on the grounds that it would result in lost business.Which of the following, if true, justifies the airlines conclusion?(A) The airlines customers prefe

55、r less congested airports.(B) It takes five minutes more flying time to reach the second airport.(C) There are fewer runways, and thus less capacity, at airport Y.(D) Airport Y is located in a region with better transport links to the final destinations of many travelers from continent B.(E) Many cu

56、stomers traveling between continent A and continentB choose certain airlines because of the easy flightconnections they offer at airport X. Sorry, the correct answer is (A). Lets look at this problem using the MBA Centers five steps.Step 1: Read the question first.Step 2: Read the argument.Step 3: P

57、araphrase the argument using your own words.Step 4: Predict the answer.Step 5: Use the process of Error Identification to eliminatethe wrong answers.Which answer choice will best weaken the arguments conclusion? Imagine a piece of new information that would destroy the argument. If necessary, transl

58、ate it into something that makes sense. Make it personal. Identify the premises, the conclusion, and the flaw (the assumption).Eliminate any answer choices that strengthen or are out of scope. Who said the plants in both groups are the same? Heres an easier oneA citys public transportation board has

59、 decided to cut costs by reducing the frequency of its bus service from an average of eight minutes to an average of ten minutes between buses. The board announced that it can do so without seriously reducing the quality of service.Which of the following statements, if true, would most strengthen th

60、e validity of the boards announcement?(A) The less frequent use of the buses will lower maintenancecosts, resulting in savings that can be used for much-neededrepairs of the citys pedestrian bridges.(B) At rush hour, congestion in the city slows bus service by thirtypercent.(C) Because of a robust e

61、conomy in the city, passenger patronage has increased substantially in recent years.(D) The public transportation board has recently gathered data onthe levels of ridership on all bus lines, showing that some linesare used by many more riders than others.(E) The contract with the bus drivers union s

62、tipulates that the citynot lay off any drivers because of reduced bus service. Right again! This ones harder stillKobayashi coffee has more caffeine than Marlowe Select coffee. But since Chula Vista coffee has more caffeine than Valentino coffee, it follows that Kobayashi coffee has more caffeine th

63、an Valentino coffee.Any of the following, if introduced into the argument as an additional premise, makes the argument above logically correct EXCEPT?(A) Marlowe Street coffee has more caffeine than Valentinocoffee.(B) Marlowe Street corree has more caffeine than Chula Vista coffee.(C) Marlowe Stree

64、t and Chula Vista coffees have the sameamount of caffeine.(D) Kobayashi and Chula Vista coffees have the same amount ofcaffeine.(E) Chula Vista coffee has more caffeine than Kobayashi coffee. Sorry, the correct answer is (E). Lets look at this problem using the MBA Centers five steps.Step 1: Read th

65、e question first.Step 2: Read the argument.Step 3: Paraphrase the argument using your own words.Step 4: Predict the answer.Step 5: Use the process of Error Identification to eliminatethe wrong answers.Which answer choice will best weaken the arguments conclusion? Imagine a piece of new information t

66、hat would destroy the argument. If necessary, translate it into something that makes sense. Make it personal. Identify the premises, the conclusion, and the flaw (the assumption).Eliminate any answer choices that strengthen or are out of scope. There you go!It has often been hypothesized that global oil consumption, which increases every year, will deplete the supply of oil, with catastrophic results for the global economy. However, these claims never stand up to scrutiny, as the volume of oil i