LSAT-Section-1-Logical-Reasoning – Section One : Logical Reasoning

Reference / correct answer:

Argument construction

The argument is simple to understand. An attorney argues that since the garage and the main door of the client's house were not bolted on the murder-night, a thief must have intruded the home to steal valuables. The client's wife would have confronted him and this led the thief to murder her. This follows that his client who is accused of the murder must be acquitted.

Flaw in the argument

The attorney's argument, simply put, is:

(Garage and main door were open) => (A Thief must have entered) => (Since a thief was present in the house that night, he must be the murderer) => (His client must be acquitted)

What is the flaw in the argument?

Only on the basis that the garage and the main door were not bolted on the murder-night, the attorney claims that the chance that a thief must have broken into the house is 100%. He does not consider that other explanations for the garage and main door not being bolted might be possible. For example, the client may have committed the murder and then himself opened the garage and the main door to make it look like the work of an outsider.

Also, what are the chances that if an outsider did come in, that outsider was a thief? Was any theft noted or reported at the client's home that night? Was a thief noticed in the vicinity of the client's home that night? The attorney provides no evidence to substantiate his claim that a thief came into the client's house that night.

Further, if a thief did come into the house and was indeed confronted by the client's wife, is there any proof of such a confrontation in the house that night? Further, is such a confrontation a sufficient reason to drive a thief to murder?

Thus, the evidence that the garage and the main door were not bolted on the murder-night does not actually absolve the attorney's client. The client can still be the culprit. The flaw in the attorney's argument is that the attorney does not even consider that there might be other explanations for the open garage and main door and presents the explanation that best serves his and his client's interests as the only one possible.

Predict a parallel argument

Upon looking at the options, we find that the options are on varied topics. So, we need to read each of them one by one and select the best option. To find the parallel flaw argument, we first need to analyze the question argument.

The evidence: The garage and the main door were not bolted on the murder-night.

The argument: The evidence suggests that there is a very high probability that a thief must have intruded into the client's home; therefore, this thief must be the murderer too and the client should be absolved of the murder charge.

The flaw: The evidence does not support the claim that there is no probability that the client committed the murder.

The argument provides evidence and concludes (from that evidence) that there is only one possible outcome and other possibilities do not exist.

We need to find an option argument that possesses the above elements.

Answer choices

[The city administration could not find a solution …] This is incorrect. The element that is not parallel to the question argument is that the city administration itself takes the blame and does not transfer the blame to another entity.

[Due to the work strike of railroads and the non-availability of sufficient buses …] This is incorrect. There is no flaw in the argument. A flawed judgment is not drawn. Since commuting by rail and bus are the only two options for John, he must have faced hard-time with commuting during the rush hours when the railroad was on strike and the number of buses was not sufficient during the rush hours.

[In the 100-meter race, Amy's co-participants won Silver and Bronze …] This is correct. Though Amy is an excellent racer, it does not mean that other participants cannot beat her in the race. They all or at least three can beat Amy. If this is so, Amy does not have a chance to win Gold. This a perfect parallel flawed argument.

[The evidence collected reveals that the financial fraud was executed …] This is incorrect. There is no flaw in the argument. The evidence suggests that either some team members or a third party may have executed the financial fraud, which is valid reasoning.

[In an annual test of Midland high school students, the average score of neither…] This is incorrect. There is no flaw in the argument. This is a quantitative argument. It tests your concept on weighted average. Note that the weighted average of the two groups' averages can neither be greater than the greater of the two averages nor be smaller than the smaller of the two averages. For example, say the number of boys = 100 and their average score = 40; the number of girls = 50 and their average score = 45. The combined average of 150 students would lie between 40 to 45, which is less than 50. Even if you swap the number of boys and the number of girls, the weighted average would still between 40 to 45 (value will not be the same), which is less than 50.

Reference / correct answer:

Argument construction

The parliamentarian states that no crime that impacts only a few victims (for example, murdering only one or two people) deserves capital punishment. Therefore, on the basis of this statement, he concludes that the capital punishment can be awarded only for the rarest of rare crimes that threaten the survival or well-being of the society as a whole.

Some people object to this conclusion and give as counterexamples such cases in which only one or two people may have been killed but which were so brutal or gruesome as to make the general population think that the murderer deserved to get capital punishment.

To this objection, the parliamentarian responds that if those cases really deserve capital punishment, then they must have hurt more than a few individual victims.

Flaw in the argument Let's dissect the argument.

The parliament' principle:

The parliamentarian decides the applicability of capital punishment for a crime by looking at the number of victims impacted by the crime. If a crime impacts only a few individual victims, then capital punishment should not be awarded.

The Parliamentarian's Conclusion/Assertion

Capital punishment should be awarded if and only if a crime impacts the survival or well-being of the whole society.

How does he support this conclusion? Simply by citing his above principle.

People's counterexample:

Gruesome crimes that impact only one or two individual victims but are generally considered to deserve capital punishment.

The parliamentarian's defense:

The counterexample doesn't ruffle the parliamentarian at all. Rather, he still uses his principle to respond to it.

He says that if the gruesome crimes that are offered as a counterexample deserve capital punishment, then they cannot have impacted only a few individuals. (Perhaps he would go down the road of showing how the families or neighborhoods of the victims were impacted too, or how those crimes destabilized the society as a whole and therefore merited capital punishment to preserve the well-being of the society etc.) What is the flaw in the parliamentarian's reasoning?

He makes a conclusion based on nothing but his self-proclaimed stance treated as the absolute and incontrovertible truth. When that conclusion is challenged by counterexamples, he again responds by citing his stance, and suggests that if those counterexamples are true, then they must adhere to his stance.

Let's analyze each option one by one.

Answer choices explanation:

[It contains an unfounded acceptance of a popular opinion.] This is incorrect. While the parliamentarian does blindly accept his stance to be true ("unfounded acceptance"), the argument does not suggest that this stance is popular and is the generally held opinion of most people.

[It relies on the parliamentarian's authority on legal or sociological matters.] This is incorrect. There is nothing in the argument that suggests that the parliamentarian exercised his authority/power to enforce his opinion.

[It seeks to convince by emotion rather than logic.] This is incorrect. There is nothing in the argument that suggests that the parliamentarian appealed emotionally to sell his opinion.

[It attempts to substantiate a viewpoint by appeal to an unrelated contemplation.] This is incorrect. The counter-argument advanced by the parliamentarian (in response to the counterexamples) is relevant to the argument.

[It assumes what it intends to substantiate.] This is correct. It is in line with the analysis done above. The parliamentarian's conclusion is rather a rephrase of his opinion.

Reference / correct answer:

Argument construction

A report (published by the United States Bureau of Economic Analysis) talks about two kinds of American workers:

Those employed in Agriculture and allied services – let's call this Group A, and Those employed in Other Sectors – let this be Group B

As per the report, in the last five years, the per capita income of:

Group A has increased by 10%

Group B has increased by 20%

From the above premises, the following conclusion is drawn: (Per Capita Income of Group B today) > (Per Capita Income of Group A today)

Flaw in the argument

Let's dissect the argument. Let's assume that 5 years ago, the per capita income of

Group A was A0

Group B was B0

Then, as per the report findings, the per capita income today of

Group A is A1 = A0 + 10% of A0 = 1.1A0

Group B is B1 = B0 + 20% of B0 = 1.2B0

The Conclusion

B1 > A1; That is, 1.2B0 > 1.1A0

We know from the question statement that this conclusion is flawed. What is the flaw in it?

In the above inequality, 1.2 is certainly greater than 1.1. However, can we be sure that B0 is greater than A0? Does the argument give us any basis to assume this? The answer to both questions is 'No.'

What if B0 were significantly smaller than A0? Say, B0 was 40,000 dollars while A0 was 60,000 dollars? Then:

B1 = 1.2B0 = 1.2 × 40,000 = 48,000 dollars

A1 = 1.1A0 = 1.1 × 60,000 = 66,000 dollars

In such a case, the conclusion drawn by the argument (B1 > A1) is proved wrong.

Therefore, the flaw in the argument is that it fails to consider the cases where B0 < A0.

Let's analyze each option one by one.

Answer choices explanation

[five years ago, fewer American workers were employed in other sectors than in Agriculture and allied services] This is incorrect. Since the comparison is between the per capita incomes of the two sectors, the number of workers in either sector is not relevant.

The value of per capita income therefore already takes into account the 'number of workers.' Had the 'total income' of the two sectors been mentioned in the argument along with their per capita incomes, then the 'number of workers' might have been a factor.

[five years ago, the per capita income of American workers employed in other sectors was significantly less…] This is correct. As per this option, the flaw in the argument is that it fails to rule out the possibility that B0 < A0. This is in-line with the discussion done in the 'Argument construction' section.

[over the last five years, the number of American workers employed in other sectors has decreased] This is incorrect. One of the ways in which the per capita income of other sectors could have increased is with decreasing number of workers; there is no reason to rule out the possibility that the increase in the per capita income happened due to this reason. Therefore, failing to rule it out does not make the reasoning questionable.

[over the last five years, many American workers who were previously employed in Agriculture and allied services shifted to other sectors] This is incorrect. Since the per capita income depends on the number of workers, the changing numbers of Groups A and B, as suggested in this option, would have impacted the respective per capita incomes of both the groups. However, this does not affect the argument at all since neither the premises nor the conclusion concern themselves with 'how or why' the per capita income of each group changed. Therefore, failing to rule out the possibility that the change in per capita income happened due to the reason suggested in this option is no error in reasoning.

[the total national income generated by Agriculture and allied services now is still greater than that generated by other sectors] This is incorrect. If the total national income generated by Agriculture and allied services was greater than that generated by other sectors five years ago and remains greater now, but the number of workers employed in Agriculture and allied services is far greater than those in other sectors, then the conclusion B > A is still possible. (For an example with easy numbers, consider

Therefore, failing to rule out the possibility of this option does not prove the conclusion wrong.