Critical Reasoning Basics
1. Logic is a system of reasoning that allows us to arrive at conclusions using available data and critically check the validity of these conclusions.
2. Argument / Stimulus: in critical reasoning we consider group of related propositions. An argument is set of two or more propositions (called premises) in such a way that all but one of them (premises) provide support for the remaining one (conclusion)
3. Line of reasoning: the transition or moment from premises to the conclusion, the logical connection between them, is called line of reasoning.
4. Assumption: the un-stated premises that make or break the conclusion of the argument / stimulus
5. Conclusion: Contains the central idea of the argument.
• Conclusion = Premises + Assumption (the one that links the premises)
• If premise are valid and sufficient, then the conclusion must be true. Conversely if the conclusion is invalid, then premises must be invalid or in sufficient or both. . . But if premises are invalid the conclusion is not necessarily invalid.
There are few categories of Critical Reasoning questions that appear on IBA admission test the most :-
A. Assumptions
• An assumption is merely an unstated (implied) premise.
• In logically correct arguments which contain an assumption, the premise + assumption = conclusion. • An assumption bridges the gap between argument’s stated premises and conclusion.
• Remember, since the assumption is an UNSTATED premise, any answer choice that comes from the passage to support your assumption is necessarily incorrect.
• For assumption questions, find the conclusion and determine which answer choice needs to be true for a conclusion to be valid.(It must be a statement that completely supports the conclusion)
QUESTION STEM EXAMPLES:
- “The argument in the passage depends on which of the following assumptions?”
- “The conclusion above is based on which of the following assumptions?”
CORRECT ANSWER CHOICES:
• Will be supporter or defender • Supporters help to link unrelated information presented in the stimulus and fill logical gaps • Defenders eliminate possibilities of weakness and attack to the stimulus/conclusion.
example: All male citizens of Athens had the right to vote. Therefore, Socrates had the right to vote in Athens.
B. Strengthen the Argument
Identify the conclusion—this is what you are trying to strengthen!
Find the logical gap and fix it with additional information. This is the ONLY type of question where additional information (outside of the question) can/should be used.
QUESTION STEM EXAMPLES:
- “Which of the following, if true, most strengthens the argument?”
- “Which of the following, if true, most strongly supports the statement above?"
- “Which of the following, if true, does most to justify the conclusion above?”
Correct answers to this question type will:
• Connect evidence with conclusion better • Make conclusion stronger. • Strengthen the evidence with new information (perhaps an assumption is needed to make the argument work)
example:
Advertisement: At most jewelry stores, the person assessing the diamond is the person selling it so you can see why an assessor might say that a diamond is of higher quality than it really is. But because all diamonds sold at Gem World are certified in writing, you’re assured of a fair price when purchasing a diamond from Gem World.
The reasoning in the advertisement would be most strengthened if which one of the following were true?
A. Many jewelry stores other than Gem World also provide written certification of the quality of their diamonds.
B. The certifications of diamonds at Gem World are written by people with years of experience in appraising gems.
C. The diamonds sold at Gem World are generally of higher quality than those sold at other jewelry stores.
D. The diamond market is so volatile that prices of the most expensive diamonds can change by hundreds of dollars
from one day to the next.
E. The written certifications of diamonds at Gem World are provided by an independent company of gem specialists.
C. Weaken The Argument
To solve these questions, you first need to identify the premise and the conclusion. In this question type, we assume an answer choice presented to be true – even if it introduces new information (obviously, the information has to be relevant to the stimulus)
QUESTION STEM EXAMPLES:
- “Which of the following, if true, most seriously weakens the argument above?”
- “Which of the following, if true, casts the most doubt on the conclusion drawn above?”
- “Which of the following, if true, most calls into question the claim above?”
ANSWER CHOICE QUALIFICATION:
• Should rebuke the conclusion of the stimulus • Answer choices are taken to be true, even if there is new information provided. • Will either break down causality or show an obvious error in reasoning in formation of the conclusion
CORRECT ANSWER CHOICES:
• Will point out an obvious reason for the illogical conclusion • Enumerate a wrong generalization • Point out improper comparisons between two scenarios that the author assumed
example: Carl is clearly an incompetent detective. He has solved a smaller percentage of the cases assigned to him in the last 3 years—only 1 out of 25—than any other detective on the police force. Which one of the following, if true, most seriously weakens the argument above?
A. Because the police chief regards Carl as the most capable detective, she assigns him only the most difficult cases, ones that others have failed to solve.
B. Before he became a detective, Carl was a neighborhood police officer and was highly respected by the residents of the neighborhood he patrolled.
C. Detectives on the police force on which Carl serves are provided with extensive resources, including the use of a large computer database, to help them solve crimes.
D. Carl was previously a detective in a police department in another city, and in the 4 years he spent there, he solved only 1 out of 30 crimes.
E. Many of the officers in the police department in which Carl serves were hired or promoted within the last 5 years
D. MUST BE TRUE/ INFERENCE/ MAIN POINT/CONCLUSION
Consider the evidence, draw a conclusion.
An inference is an extension of an argument, not a necessary part of it.
A valid inference is a conclusion, but not necessarily the conclusion, of a set of statements.
For inference questions, determine which answer choice must absolutely, positively be true based on what you’ve read.
• Pick the obvious answer choice. • Avoid extreme answers (too strong or too weak)
CORRECT ANSWER CHOICES:
• Restatement of the conclusion • Combination of one or more premises • Should be the main point of the stimulus, not just a premise (for Main Point questions-Repeat premises are wrong )
E. Evaluate the Argument
-The question stem will likely use some form of the word “evaluate,” “determine,” or “useful / important to know.”
-Find the conclusion and identify the main supporting premise. If you can articulate any gaps between the main premise and the conclusion, do so. Think of the conclusion as the author’s hypothesis; your job is to find the answer choice that can test that hypothesis. The answers will provide a “whether or not” type of statement, indicating information that might or might not be so. The correct answer will be able to both slightly strengthen and slightly weaken the hypothesis, depending upon whether the information in that choice is true or is not true.
-Know what you’re not trying to do as well. We’re not trying to strengthen the conclusion or make it more likely that the author’s hypothesis is correct
E. Flaw in reasoning
Flaw in the reasoning questions asks to find or determine the error of reasoning in the author's argument.
QUESTION STEM EXAMPLES:
- “Which of the following most accurately describes a flaw in the argument's reasoning?”
- “The reasoning above is flawed because it fails to recognize that.”
Few tips:
>Understand structure of argument. Identify premise (P), conclusion (C) and any unstated assumptions. Look for structural signpost words which mark P and C.
>To distinguish between conclusion and evidence ask "what does the author believe" (conclusion) OR "why does the author believe" (Evidence)
>Fight your habit to make assumptions regarding arguments and watch out for illogical connections the test wants you to make!
>Don’t assume information unless you see it in the argument.
>Answer question being asked.
Practice Questions
- Most young employees move quickly from one company to the next, changing jobs up to three times in a year. However, Happy Snax is known for retaining young workers for well over a year. Happy Snax claims its retention rate is due to the fact that they do not require uniforms or formal break times.
Which of the following, if true, most strengthens Happy Snax explanation of its success in retaining young employees?
A) Young employees often change jobs because they become bored with their current job and are looking for something new and exciting
B) Many young employees at Happy Snax have not had a job previously
C) Young employees find uniforms and formal schedules unappealing
D) Uniforms and formal schedules lead to more productivity in the workplace
E) Happy Snax also provides free housing to all of its young employees for the first year
- An airplane engine manufacturer developed a new engine model with safety features lacking in the earlier model, which was still being manufactured. During the first year that both were sold, the earlier model far outsold the new model; the manufacturer thus concluded that safety was not the customers’ primary consideration.
Which of the following, if true, would most seriously weaken the manufacturer’s conclusion?
(A) Both private plane owners and commercial airlines buy engines from this airplane engine manufacturer.
(B) Many customers consider earlier engine models better safety risks than new engine models, since more is usually known about the safety of the earlier models.
(C) Many customers of this airplane engine manufacturer also bought airplane engines from manufacturers who did not provide additional safety features in their newer models.
(D) The newer engine model can be used in all planes in which the earlier engine model can be used.
(E) There was no significant difference in price between the newer engine model and the earlier engine model.
- Over the past six years, most of the students in Tupac city have regularly attended colleges in the neighbouring Mekon city to pursue their graduate degrees. However, according to a recent change in the education policies of Mekon city, the colleges in Mekon city are expected to increase their fees to almost the same level as those charged by colleges in Tupac city. Therefore, it can be safely concluded that colleges in Tupac city will see a surge in the number of students enrolling with them to pursue their graduate degrees.
Which of the following is an assumption on which the argument depends?
(A) The teachers at colleges in Mekon city are generally considered better than those at colleges in Tupac city.
(B) Tupac city does not have good quality colleges.
(C) The low fees charged by colleges at Mekon city is the primary reason why students from Tupac city move to these colleges.
(D) Students who study at colleges in Tupac city do not perform better than those who study at colleges in Mekon city.
(E) Mekon city does not have more colleges than Tupac city.
- When three Everett-owned Lightning-built airplanes crashed in the same month, the Everett company ordered three new Lightning-built airplanes as replacements. This decision surprised many in the airline industry because, ordinarily when a product is involved in accidents, users become reluctant to buy that product.
Which of the following, if true, provides the best indication that the Everett company’s decision was logically well supported?
(A) Although during the previous year only one Lightning-built airplane crashed, competing manufacturers had a perfect safety record.
(B) The Lightning-built airplanes crashed due to pilot error, but because of the excellent quality of the planes there were many survivors.
(C) The Federal Aviation Association issued new guidelines for airlines in order to standardize safety requirements governing preflight inspections.
(D) Consumer advocates pressured two major airlines into purchasing safer airplanes so that the public would be safer while flying.
(E) Many Lightning Airplane Company employees had to be replaced because they found jobs with the competition.
- Homeowners aged 40 to 50 are more likely to purchase ice cream and are more likely to purchase it in larger amounts than are members of any other demographic group. The popular belief that teenagers eat more ice cream than adults must, therefore, be false.
The argument is flawed primarily because the author
(A) fails to distinguish between purchasing and consuming
(B) does not supply information about homeowners in age groups other than 40 to 50
(C) depends on popular belief rather than on documented research findings
(D) does not specify the precise amount of ice cream purchased by any demographic group
(E) discusses ice cream rather than more nutritious and healthful foods
- A certain pharmaceutical firm claims that its dietary supplement, Dietol, is highly effective in helping obese people lose weight and improve physical endurance. The company supports this claim by providing the results of a recent experiment that involved over 800 subjects suffering from obesity. During the 9-week experiment, each of the subjects was required to take a regular dose of Dietol every day immediately after their daily 2-hour workouts supervised by a professional fitness instructor. As a result of the experiment, the subjects lost an average of 12 pounds of weight per person, and over 95% of all participants demonstrated higher physical endurance.
The answer to which of the following questions would be most helpful in evaluating the conclusion of the pharmaceutical company?
A. What was the daily dose of Dietol that the subjects were required to take?
B. What was the maximum weight lost by any participant during the 9-week program?
C. What would be the average weight loss and the improvement in endurance in a group of subjects with similar characteristics involved in the same physical fitness program but not taking Dietol?
D. What was the average age among the subjects participating in the experiment?
E. Did the majority of subjects experience a significant improvement in physical strength?
- At present the Hollywood Restaurant has only standard-height tables. However, many customers come to watch the celebrities who frequent the Hollywood, and they would prefer tall tables with stools because such seating would afford a better view of the celebrities. Moreover, diners seated on stools typically do not stay as long as diners seated at standard-height tables. Therefore, if the Hollywood replaced some of its seating with high tables and stools, its profits would increase.
The argument is vulnerable to criticism on the grounds that it gives reason to believe that it is likely that
(A) some celebrities come to the Hollywood to be seen, and so might choose to sit at the tall tables if they were available.
(B) the price of meals ordered by celebrities dining at the Hollywood compensates for the longer time, if any, they spend lingering over their meals.
(C) a customer of the Hollywood who would choose to sit at a tall table would be an exception to the generalization about lingering
(D) a restaurant's customers who spend less time at their meals typically order less expensive meals than those who remain at their meals longer
(E) with enough tall tables to accommodate all the Hollywood's customers interested in such seating, there would be no view except of other tall tables.
- The rise in free, do-it-yourself instructions on the Internet for home repairs has led to a decrease in revenue for home service technicians and an increase in the number of injuries caused by people who have attempted home repairs themselves. Unfortunately, not all of the do-it-yourself instructions on the Internet are written as well as they should be.
Which of the following can be inferred from the argument above?
(A) The number of people who are not home repair technicians and who have been injured while attempting home repairs has increased.
(B) Most people who are injured while attempting home repairs have done so while following instructions found in free do-it-yourself instructions on the Internet.
(C) The overall sale of online do-it-yourself home repair instructions by home service technicians has not been equal to the loss of revenue the technicians have incurred due to free offerings of this sort of material.
(D) Most free do-it-yourself home repair instructions found on the Internet do not provide enough clear information regarding safety precautions.
(E) As more free do-it-yourself instructions for home repairs are made available on the Internet, home service technicians will suffer more losses in revenue.
- Which of the following most logically completes the passage?
For the past several years, a certain technology has been widely used to transmit data among networked computers. Recently two data transmission companies, Aptron and Gammatech, have each developed separate systems that allow network data transmission at rates ten times faster than the current technology allows. Although the systems are similarly priced and are equally easy to use, Aptron's product is likely to dominate the market, because __________.
(A) Gammatech has been in the business of designing data transmission systems for several years more than Aptron has
(B) the number of small businesses that need computer networking systems is likely to double over the next few years
(C) it is much more likely that Gammatech's system will be expandable to meet future needs
(D) unlike many data transmission companies, Aptron and Gammatech develop computers in addition to data transmission systems
(E) it is easier for users of the current data transmission technology to switch to Aptron's product than to Gammatech's
- It is difficult to keep deep wounds free of bacteria. Even strong antibiotics fail to kill the bacteria that live in such wounds. However, many physicians have succeeded in eliminating bacteria from deep wounds by packing the wound with a sweet substance like sugar.
Which one of the following, if true, most helps to explain why treating deep wounds with sugar as described above is successful?
(A) Bacteria that live in deep wounds thrive in a moist environment, and sugar has a dehydrating effect.
(B) Sugar that is nearly pure is readily available for use in medical treatments.
(C) Many kinds of bacteria can use sugar as a nutrient and will reproduce rapidly when sugar is available to them.
(D) Some foods that contain sugar can weaken the effects of certain antibiotics.
(E) Strong antibiotics were developed only recently, but the use of sugar as a treatment for wounds dates back to ancient times.