Explain (Critical Reasoning) for GMAT Notes | Study Verbal for GMAT - GMAT

Introduction to GMAT Critical Reasoning

GMAT Critical Reasoning is a question type found in the GMAT Verbal section. In CR questions, the prompt presents some sort of argument. Then you need to analyze the argument—for example, by strengthening it, weakening it, finding its underlying assumption, etc.  You’ll find around 13 Critical Reasoning questions in the GMAT Verbal section.
Although you do have to read a prompt in GMAT Critical Reasoning, CR tests your critical thinking and logic skills more than your reading skills. In fact, many would argue that the CR questions are a logical reasoning test within the GMAT verbal section. The argument prompt is typically less than 100 words, much shorter than a Reading Comprehension passage, and there’s always only a single question on the Critical Reasoning argument.  Critical Reasoning makes up roughly 1/3 of the Verbal Section, about 13 Critical Reasoning questions of the total of 41 Verbal Questions.

Why does the GMAT ask Critical Reasoning questions?

• You are preparing for the GMAT, which ostensibly means you are planning on attending business school, and this in turn suggests that you are anticipating a management career in some aspect of the business world. The entire business world runs on buying and selling: even if you are not a salesperson yourself, the success of your business, in a sense the raison d’etre of the business, depends on the money it will make from sales. 
• In its essence, every sale is an argument. If I want to sell you something, I have to convince you to buy it. If I make a wonderfully cogent argument, I may well generate the sale.  If my argument is faulty, and I repeat this pattern, that can only mean bad things for the long-term financial well-being of my business. 
• Every sale is an argument, but that’s just where the arguments in the business world start. How does your company decide whether one strategy or policy is better than another? What motivates your company to buy from a supplier? What motivates your customers to continue buying from you? What concerns does your insurance company have about your company? What concerns do your company’s investors have? All of these important points, and many more, will be settled by arguments. 
• A typical manager has to deal with arguments from all quarter all day.  An effective manager has to be skilled at deciding: how would I strengthen or weaken this argument?  what is the assumption of this argument? what further evidence would I need to evaluate this argument? In other words, a real-life manager needs to apply all the skills required for Critical Reasoning on the GMAT. Arguments are very important in business, and the skill of evaluating arguments is one that every manager should cultivate. That’s precisely why business schools want you to bone up on it, which is why the GMAT asks about it in Critical Reasoning questions.

The 8 Types of CR Questions

Step one of the general strategy for GMAT Critical Reasoning is: read the question before reading the argument.  Know which type of question you are going to have to answer, and read the argument with that question in mind.  
The eight broad categories of GMAT Critical Reasoning questions are

• weaken the argument/find the flaw in the argument
• strengthen the argument
• find the assumption (know the Negation Test)
• 4) draw inference/conclusion
• structure of the argument, including boldface structure questions and dialogue structure questions
• paradox
• evaluate the conclusion
• complete the argument

Know What You’re Looking For

• In all Critical Reasoning questions, the GMAT gives one correct answer and four tempting and potentially confusing statements for the other choices.  Folks who read the argument & question and then wander aimlessly into the answer choices without any further thought are asking to be perplexed, and, chances are, they spend much longer than necessary on many Critical Reasoning questions.
• Go into the question with an idea of what you seek.  For types #1-3, the best thing to do is to find the assumption of the argument — reaffirming or undercutting the assumption of an argument is the most powerful way to strengthen or weaken it. Finding the assumption may also be helpful in find the flaw of the argument (if the flaw is a faulty assumption).
• For the other question types, you will be less able to predict what the answer will be; still, formulating the task in your own words will help you.  In your own words, what is the structure of the argument? What is the paradox that needs to be resolved? What kind of information would be required to evaluate the conclusion? etc.  The more clearly you understand what type of information or argument will satisfy the question, the more quickly you will find it.
• If you can integrate these strategies, you will be able to crack GMAT Critical Reasoning questions faster and more accurately.

Examples

Q.1. Lauren is clearly going to make an awful professor. Nearly half of her students failed their final this past spring. She should probably choose another career path, because her students’ performance demonstrates that she doesn’t teach very well.
What statement, if true, most weakens the argument above?
(a) This was Lauren’s second time teaching a college class.
(b) The class Lauren was teaching is a required class for all freshmen.
(c) The students who failed the exam also had poor attendance.
(d) The students who passed the exam attended an optional review session Lauren’s teaching assistant held.
(e) Lauren struggled early in the semester with lesson planning.

Correct answer is option (c)
C is correct because this shows that the students' poor attendance, and not Lauren's teaching style, was likely to blame for their poor performance on the exam. If they were not in class when Lauren was teaching, her style could have very little positive or negative impact on their learning.
A is incorrect because we do not know if Lauren's students did better, worse, or the same in the previous class than in this one.
B is incorrect because the class being required would have no direct impact on how students would do on a single exam.
D is incorrect because it speaks to the motivation of the students, and perhaps the teaching effectiveness of the TA, not Lauren herself.
E is incorrect because it supports that idea that Lauren has had issues with teaching effectiveness.

Q.2. Gina doesn't understand why she cannot get a job as a computer engineer. She even went back to school and got a degree in computer science. After two years on the job market with only a few interviews and no offers, she is staring to wonder if she is not getting hired because she is a woman. One of her friends told her that women seldom succeed in technology fields, and she is beginning to believe it.
Which of the following, if true, most weakens the argument above?
(a) Gina got her degree online.
(b) All the people Gina has interviewed with have been men.
(c) Gina had both female and male professors in college.
(d) Gina graduated with a C average.
(e) Gina interviews very well.

Correct answer is option (d)
D is correct because it indicates that Gina's grades and knowledge of the field, not her sex, are likely behind her failure to get hired.
A is incorrect because whether her degree was earned online or not likely matters little; hiring managers probably don't even know whether her degree was earned online.
B is incorrect because, while it indicates that there are many men in the field, Gina has had only a few interviews. These experiences do not mean that women are not hired.
C is incorrect because it indicates that both men and women teach in the field, thus that women get hired.
D is incorrect because while she might interview well, this does not guarantee an offer when weighed against other factors on her resume.

Q.3. Sarah: "I don't understand why you recycle so much. The recycling program costs the city several million dollars a year. Trash disposal at the landfill costs half as much per household than the municipal recycling program. It just doesn't seem cost effective to have a recycling program."
Lauren: "The point of recycling isn't to save money. By recycling, we keep thousands of tons of materials out of our landfills, which mean we can use the same landfills longer. It's about conserving our resources, not about saving money on trash pickup."
Lauren's response to Sarah serves to
(a) Support Sarah’s contention that recycling is too expensive.
(b) Refute Sarah’s argument that recycling is more expensive than taking trash to the landfill.
(c) Suggest to Sarah that there is an alternate view of why recycling makes good sense for the people of their city.
(d) Points to a fundamental value difference between the two when it comes to conservation.
(e) Points out her ignorance of municipal finances.

Correct answer is option (c)
C is correct because Lauren agrees that the recycling program is expensive, but she is seeking to point out that the cost of the program is only one concern when looking for ways to deal with waste in their city.
A is incorrect because, while Lauren agrees that the program is expensive, she points out other ways in which it is valuable.
B is incorrect because Lauren agrees with Sarah that the program is expensive, though she is trying to refute Sarah's claim that it is therefore not a good program.
D is incorrect because we cannot tell from Sarah's statement what her values around conservation are. Laurens' seem clear from her reply, but it is possible both have similar values around this issue.
E is incorrect because Lauren seems quite well informed about municipal finances – she does not dispute Sarah's statements about the costs of recycling and waste disposal.

Q.4. Jensen Strawberry Farms in Central Texas went organic two years ago. The first year, they had a bumper crop of strawberries and could barely keep up with the demand from local restaurants and markets. This year, however, their yield fell by more than 50%. The Jensens are now considering going back to conventional farming, since organic farming does not appear to be sustainable.
Which of the following, if true, weakens the argument above?
(a) It takes up to three years for traces of some pesticides used on strawberries to leave the soil.
(b) Other organic strawberry farms in California and Oregon produced larger-than-normal crops this year.
(c) Organic lettuce farms near to Jensen Strawberry Farms also saw a lower-than-normal yield this year.
(d) Central Texas experienced temperatures above 100 degrees and had no rain for 75 straight days this year.
(e) Jensen Strawberry Farms got its crop in a week earlier this year than last year.

Correct answer is option (d)
D is correct because the heat and drought, rather than the organic methods, are likely the cause of lower yields. Thus, the claim that organic farming is not sustainable cannot be supported.
A is incorrect because we do not know if Jensen Farms used any of those pesticides, nor if traces of those pesticides would have impacted this year's yield.
B is incorrect because we do not know how the weather in these states compares to that in Texas, or how these farms otherwise compare to Jensen.
C is incorrect because the lower yields at neighboring lettuce farms would seem to point to organic methods as the reason for lower yields, but we do not have enough information about these other farms to make that connection.
E is incorrect because we do not know if getting the crop in earlier caused it to grow more slowly, more quickly, or be otherwise impacted.

Q.5. According to latest research by some professors at Michigan State University, Ozone layer depletion is one of the major causes of Global Warming. Also, because of ozone depletion, there are some noxious rays which enter the earth's environment and cause permanent eye infection in some animals.
Which of the following options support the above stated argument?
(a) All wavelengths are not harmful for eyes
(b) Human eyes are not infected by harmful wavelengths
(c) Very few species of animals are exposed to these harmful wavelengths of light
(d) Some harmful radiations can easily enter earth’s environment due to ozone depletion
(e) Due to global warming, the temperature of the earth is increasing which in turn cause eye infection in some species of animals

Correct answer is option (d)
As stated in the question, "because of ozone depletion, there are some noxious rays which enter the earth's environment and cause permanent eye infection in some animals".
Option E might seems as the correct option, but if you read carefully, it declares global warming as the cause of eye infections, which in fact is incorrect. It's the ozone depletion which allows the noxious rays to enter the earth's environment.