Verbal Lecture-09
Flaw in logic:
These questions are close cousin of Method of reasoning questions. In method of reasoning questions, the question asks you to describe method that the author used to convey his point in the argument. The flaw in logic asks you to take the next level of understanding and describe the flaw in logic of the argument. You have to think why the argument is flawed contains illogical reasoning. These questions are usually difficult, so if you perform well in your exam, you may see such questions frequently after that.
Let’s understand this question type with example.
University of California Berkley has more number of students who completed graduation than Yale University. Therefore, graduation rate in University of California Berkley must be higher than that of Yale University.
What is the flaw in the author’s reasoning?
Answer explanation:
Self-Analysis:
The argument first mentioned some statistical data about number of students who graduated in two universities. From this, the author made his point that university with higher number of graduated students must have higher graduation rate. Is that make a sense? No it does not!
Firstly, we know that graduation rate equals to the number of students who completed graduation divided by total number of students who are eligible to graduation. i.e:
Here notice that the denominator includes number of students eligible for graduate, whose information is not provided regarding both universities. So it is likely that higher number of graduated students may lead towards less graduation rate. In other words, number of graduated students and graduation rate might be inversely proportional. So that is the flaw in this argument. The author concluded his point based on insufficient information. He draws his conclusion without considering number of students who are eligible for graduation.
For instance,
Number of students graduated from University of California Berkley = 100
Number of students graduated from Yale University = 50
But,
Number of students eligible for graduation in University of California Berkley = 200
Number of students eligible for graduation in Yale University = 50
Clearly, graduation rate in University of California Berkley will be 50% while graduation rate in Yale University is 100%. Thus the author has drawn conclusion based on insufficient information. Conclusion is a statement that is MUST be true, unless mentioned in wording (i.e graduation rate COULD be greater).
There may be several reasons for flaw in logic of the argument. Let’s discuss some frequently used of these:
Improper Comparison:
This is one of the most common type of flaw in logic questions. Here, the author compare two variables that are not comparable at all or comparable only under some situations when some conditions are met. For instance, as discuss earlier, the number of graduated students cannot be compared with graduation rate but only when we have information about students who eligible for graduation.
Similarly,
Last year, on identifying several polio patients, Government of Pakistan has spent $5M in polio awareness program to acknowledge the public about this disease to avoid prevention of its spread to next generation. Presently, many dengue patients are identified. Therefore, Government of Pakistan must start another similar awareness program to prevent the spread of this new disease to next generation.
What is the flaw in logic of the argument above?
Answer explanation:
Self-Analysis:
The author took historical data from the polio patients and then extrapolate it to dengue patients. Here the assumption is that the campaign that was succeeded in prevention of polio disease will also be succeeded in prevention of dengue disease. But this assumption is not MUST be true. For instance, if dengue disease can easily and be cure via cheap medication. Then the campaign regarding prevention of dengue disease may waste the money. So a technique which was helpful for one disease prevention is not necessarily helpful for other disease prevention as well. That is the flaw.
Thus, the flaw in logic is that the author incorrectly compared two campaigns for different diseases prevention that may not give similar results.
Correlation leading Causality:
In such arguments, author takes two events that happen as a happenstance and makes his point that one of the event is due to the other. This point is drawn only on the ground that the two events happen in such a way that it looks like one event cause the other, but infect it may be wrong. The author establish causality between seemingly unrelated events. For instance,
It has been observed many times that whenever John support Team A to play against Team B, Team B win the match. Therefore Team B should encourage John to support Team A.
Here the author believe that Team B win because John has supported Team A, so these correlated events are actually causal events. This belief is flawed because when two events happen for some times in past, it not necessarily happen again in future. There might be other reasons for Team B winning. It might be just a happenstance that John had supported Team A when Team B won. It may be because Team B is better than Team A. So the support of John to Team A is not necessarily the cause behind Team B winning.
Draw conclusion based on limited sample tests:
Let’s take an example:
Abraham took 2 practice tests and scored 99 percentile. Therefore, he will score 99 percentile in his actual exam.
In this argument, the author draws conclusion based on limited sample tests.
Similarly,
The financial position of bank A in city X is in worse condition. Therefore, the bank A is in worse condition.
Here, again the author assumes that financial position of bank in city X is similar to overall financial position of the bank in the globe. This is a flaw in the argument.
Failure to have broad perspectives:
Sometimes the author adopt a very narrow thought process to make his point. These argument, therefore, may be flawed because author fail to consider the other perspectives. For instance,
The average number of graduate students in a university in country X is 1000. University A, which is situated in country X has total 50 graduate students at present. Therefore, University A student enrollment has reduced at present.
Here the author failed to consider other perspectives while deciding whether the University A student enrollment reduced at present. In fact, University A student enrollment might have increased at present from 35 graduates to 50 graduates. Thus author missed some other perspectives while making his point.
Let’s discuss another example question:
Mr A: Capitalism is harmful for the whole economy and especially for poor ones. It leads towards inflation that reduce living standard. For instance, the annual average house rents has become double in two decades.
Mr B: Capitalism has also given much more benefits. For instance, during the same period of two decades, the average annual salary has quadrupled.
Mr A argument is flawed because:
A. He assumes that purchasing power of the people in two decades has increased.
B. He does not specify the degree to which people are in worse condition now as compared to two decades ago.
C. He does not consider the number of people living below poverty line two decades ago and at present.
D. He does not consider number of people who live in rents two decades ago and at present.
E. He does not consider to compare the benefits of capitalism with the harms of capitalism while making his point.
Answer Explanation:
Self-Analysis:
Mr A only considered only a negative aspect of Capitalism while ignored a very good positive aspect. However, Mr B bring his focus on a positive aspect, an aspect that Mr A failed to consider.
Clearly from self-analysis, you can directly go the the correct answer choice, which is E. Only this choice identify the flaw in the argument.
Difference between Flaw |& weaken questions:
Flaw in logic:
1. Here we need to explain WHY the argument is flawed.
2. It is argument structure based (as mentioned a close cousin of Method of reasoning).
3. It does not contain new information
4. The correct choice in flaw question will state the flaw that exists in the argument.
Weaken questions:
1. Here we need to point out the flaw in the argument.
2. It is argument meaning based. (i.e here you need to give more focus on meaning than the argument structure).
3. It must contain new information.
4. The correct choice will state any new information that will breakdown the conclusion.
Useful to evaluate argument:
Such questions are asked at high difficulty level. These questions tests your ability to identify additional information that will help whether the argument is valid. These questions are close cousin of assumption questions. But in assumption questions, we were looking for the gap that works as bridge between premises and conclusion. While in evaluate argument questions, we will check whether that creating that bridge is feasible according to the given information in the argument.
Let’s take an example to understand this concept:
David has his exam two weeks ahead. He want to get at least 80th percentile. In a practice test, he was on 80th percentile in quantitative section, while 50th percentile on verbal section. Based on this performance in practice tests, his instructor advised him to give 75% of preparation time to verbal section, while 25% of time to quantitative section. So he can improve his verbal percentile to at least 80th percentile.
What information is useful to evaluate the argument above?
I. Whether the practice test that David attempted is sufficient enough to give correct information about David performance in actual exam.
II. Whether his quantitative section score will reduce if David give much more time to verbal section preparation.
III. Whether just by improving his verbal score, David can get at least 80th percentile in his exam.
Explanation:
In order to prove that the Instructors advise is handy, we need to evaluate the argument and find out information that helps to answer whether the Instructor’s advise is handy or not handy. If the answer is in YES, it will either validate or completely breakdown the conclusion. So if either of the two things happen, the choice is correct answer. So let’s check each choices one by one.
Choice I: If we answer it YES, it clearly validate the conclusion; hence it is correct choice.
Choice II: By answering it YES, the conclusion gets breakdown; thus it is also correct choice.
Choice III: If we answer it YES, it clearly validate the conclusion; therefore it is correct choice.
Notice that these questions test your ability to identify the assumption made by the author. To illustrate this, let’s consider another example scenario:
German workers are more efficient than African workers. Therefore, if a company want to make highly efficient automobile, it must hire German engineers.
Assumption statement 1: African engineers produce less efficient automobile than German engineers.
Evaluate statement 1: Whether German engineers can produce more efficient automobile than African engineers.
Assumption statement 2: If a country has highly efficient workers, it must also has highly efficient engineers.
Evaluate statement 2: Whether high efficient workers lead to high efficient engineers.
Assumption statement 3: Germany has most efficient workers in the world.
Evaluate statement 3: Whether any other country has more efficient workers than Germany.
These questions usually asked in following wordings:
Which of the following is useful to access the author’s claim?
Which of the following must be clarify in order to evaluate the argument?
The relevancy of which of the following is crucial in investigating the author’s position in the argument?
In order to authenticate the author’s claim, which of the following is important to know?
etc…