Taken together, some 2,000 stocks recommended on a popular television show over the course of the past 12 years by the show’s guests, most of whom are successful consultants for multibillion-dollar stock portfolios, performed less successfully than the market as a whole for this 12-year period. So clearly, no one should ever follow any recommendations by these so-called experts.

Summarize Argument
The author concludes that no one should take the advice of so-called expert stock consultants. This is because 2,000 of the stocks such experts recommended on a TV show over the last 12 years performed worse than the market did over the same period.

Notable Assumptions
The author assumes that these 2,000 stocks are reflective of what the consultants recommend in general, without considering other stocks that may have also been recommended and performed well. The author also assumes that performance over this certain 12-year period is sufficient to draw conclusions about the consultants’ abilities to predict which stocks will do well. Perhaps the period in question was anomalous for some reason, or perhaps the stocks won’t pay off until a later date.

A
Taken together, the stocks recommended on the television show performed better than the market as a whole for the past year.
Evidently, it’s sometimes a good idea to take the consultants’ advice. Last year, their stocks outperformed the market.
B
Taken together, the stocks recommended on the television show performed better for the past 12-year period than stock portfolios that were actually selected by any other means.
Since you can’t buy the market itself, you have to put together a portfolio. Those portfolios all performed even worse than those selected by the consultants, meaning their advice was worthwhile.
C
Performance of the stocks recommended on the television show was measured by stock dividends, whereas the performance of the market as a whole was measured by change in share value.
The way the stocks and the market were measured differed. This means a comparative conclusion can’t be drawn about them.
D
Performance of the stocks recommended on the television show was measured independently by a number of analysts, and the results of all the measurements concurred.
Several different measurements confirmed the stocks recommended on the TV show performed worse than the market. This certainly doesn’t weaken the claim that the so-called expert consultants aren’t giving good advice.
E
The stock portfolios for which the guests were consultants performed better for the past 12-year period than the market as a whole.
Even if the recommended stocks didn’t all do well together, the consultants were nevertheless able to create decent portfolios using different combinations of stocks. This suggests their advice may be worthwhile.

89 comments

Some plants have extremely sensitive biological thermometers. For example, the leaves of rhododendrons curl when the temperature of the air around them is below 0(C (Celsius). Similarly, mature crocus blossoms open in temperatures above 2(C. So someone who simultaneously observed rhododendrons with uncurled leaves, crocuses with mature but unopened blossoms, and a thermometer showing 1(C could determine that the thermometer’s reading was accurate to within plus or minus 1(C.

Summarize Argument
The author concludes that someone observing two separate plant phenomena would be able to determine that a thermometer reading is correct to within plus or minus one degree celsius.

Notable Assumptions
The author assumes that air temperatures are consistent in the observed area. Since crocuses open above two degrees, the temperature around the crocuses has to be below two degrees for the crocuses. But the rhododendrons would remain uncurled at any temperature above zero degrees, which means the air around them could be well above two degrees.

A
Neither rhododendrons nor crocuses bloom for more than a few weeks each year, and the blossoms of rhododendrons growing in any area do not appear until at least several weeks after crocuses growing in that area have ceased to bloom.
This is saying that our hypothetical is impossible, but that doesn’t matter. We’re concerned about weakening the argument using the hypothetical.
B
Many people find it unpleasant to be outdoors for long periods when the temperature is at or about 1(C.
Again, we’re dealing with a hypothetical. We don’t care whether the hypothetical thermometer-holder likes being out in the cold.
C
The climate and soil conditions that favor the growth of rhododendrons are also favorable to the growth of crocuses.
It doesn’t matter how these plants grew. We care about a specific instance of using the plants’ biological thermometers to test a real thermometer.
D
Air temperature surrounding rhododendrons, which can grow 12 feet tall, is likely to differ from air temperature surrounding crocuses, which are normally only a few inches high, by more than 2(C, even if the two plants are growing side by side.
Since the air temperature surrounding the two plants is likely to differ, we can’t use the plants’ reactions to the temperature to gauge if the thermometer reading is right. The plants might be reacting to different temperatures.
E
Certain types of thermometers that are commonly used to measure outdoor temperatures can be extremely accurate in moderate temperature ranges but much less accurate in warmer or colder temperature ranges.
We don’t know what a “moderate” temperature is. Zero degrees? Twenty degrees? Besides, we’re using the plants’ reactions to the temperature to gauge if the thermometer is accurate. That’s the whole point of the hypothetical.

65 comments

Concerned citizen:
The mayor, an outspoken critic of the proposed restoration of city hall, is right when he notes that the building is outdated, but that the restoration would be expensive at a time when the budget is already tight. We cannot afford such a luxury item in this time of financial restraint, he says. However, I respectfully disagree. The building provides the last remaining link to the days of the city’s founding, and preserving a sense of municipal history is crucial to maintaining respect for our city government and its authority. So to the question, “Can we really afford to?” I can only respond, “Can we afford not to?”

Summarize Argument: Counter-Position
The citizen concludes that the mayor is incorrect that the city can’t afford to restore city hall, which would strain the city’s limited budget. In support, the citizen explains that the building is the last link to the time of the city’s founding, and that preserving history helps to maintain respect for the city government. This supports the sub-conclusion that the city can’t afford not to restore city hall.

Identify and Describe Flaw
This is an “equivocation” flaw, where the same word is used in two different ways. The citizen rejects the mayor’s point about financial “affordability.” This is supported with an appeal to cultural or historic “affordability.”

A
The argument is solely an emotional appeal to history.
The citizen’s appeal to history isn’t solely emotional, because it also includes the claim that history helps to maintain the city’s authority, which is a more pragmatic consideration.
B
The argument ambiguously uses the word “afford.”
The mayor’s claim that the city can’t “afford” the restoration refers to financial affordability. The citizen’s question of whether the city can “afford” not to restore the building refers instead to cultural or historic considerations, sidestepping the mayor’s point.
C
The argument inappropriately appeals to the authority of the mayor.
The citizen doesn’t appeal to the mayor’s authority—especially because the argument is aimed at discrediting the mayor’s position!
D
The argument incorrectly presumes that the restoration would be expensive.
The citizen accepts the mayor’s point that the restoration would be expensive, but there’s no reason to think that claim is incorrect.
E
The argument inappropriately relies on the emotional connotations of words such as “outdated” and “luxury.”
The citizen’s argument doesn’t rely on words such as “outdated” and “luxury” at all. Those words are part of the mayor’s argument, with which the citizen disagrees.

57 comments

Sarah: Some schools seek to foster a habit of volunteering in their students by requiring them to perform community service. But since a person who has been forced to do something has not really volunteered and since the habit of volunteering cannot be said to have been fostered in a person who has not yet volunteered for anything, there is no way this policy can succeed by itself.

Paul: I disagree. Some students forced to perform community service have enjoyed it so much that they subsequently actually volunteer to do something similar. In such cases, the policy can clearly be said to have fostered a habit of volunteering.

Summarize Argument: Counter-Position
Paul concludes that the policy can foster a habit of volunteering in students. As evidence, he points out that sometimes when students are forced to participate in community service, those students subsequently actually volunteer to do something similar.

Describe Method of Reasoning
Paul counters the position held by Sarah. He does this by introducing a consequence of forced volunteering that Sarah did not consider: sometimes when students are forced to volunteer they enjoy it so much that they actually volunteer on their own.

A
He argues that Sarah is assuming just what she sets out to prove.
Paul does not argue that Sarah’s reasoning is circular. Rather, Paul introduces a consideration that Sarah’s argument does not consider.
B
He argues that Sarah’s conception of what it means to volunteer excludes certain activities that ought to be considered instances of volunteering.
Paul does not claim Sarah is excluding certain activities from being counted as volunteering. Rather, Paul claims that Sarah’s argument excludes the possibility of students volunteering on their own after first having been forced to volunteer.
C
He introduces considerations that call into question one of Sarah’s assumptions.
Sarah’s assumption is that by forcing a person to volunteer, that person will never actually volunteer on their own accord. Paul counters this by describing some instances where students afterwards volunteer on their own because they enjoyed it.
D
He questions Sarah’s motives for advancing an argument against the school policy.
Paul is not questioning Sarah’s motives. He question’s Sarah’s arguments on its merits instead of focusing on Sarah’s personal characteristics.
E
He argues that a policy Sarah fails to consider could accomplish the same aim as the policy that Sarah considers.
Paul does not introduce an alternative policy. Instead, he points out a consequence Sarah’s argument does not consider.

15 comments

If this parking policy is unpopular with the faculty, then we should modify it. If it is unpopular among students, we should adopt a new policy. And, it is bound to be unpopular either with the faculty or among students.

Summary

If the policy’s not popular with faculty, then we should modify it (or, by contrapositive, if we shouldn’t modify the policy, then it must be popular with faculty).

If the policy’s popular with faculty, it’s bound to be unpopular with students. (And if it’s popular with students, it’s bound to be unpopular with faculty. Popularity with one group implies unpopularity with the other.)

If the policy’s not popular with students, we should adopt a new policy.

Notable Valid Inferences

If we shouldn’t modify the existing policy, we should adopt a new policy.

If the policy’s popular with faculty, we should adopt a new policy.

If the policy’s popular with students, we should modify the policy.

A
We should attempt to popularize this parking policy among either the faculty or students.

The stimulus doesn’t suggest that any one scenario is more desirable than another. There’s no indication that the existing policy should be popular with either group, or that there’s something undesirable about the policy being unpopular.

B
We should modify this parking policy only if this will not reduce its popularity among students.

This says that modifying the policy is sufficient for not reducing its popularity among students. There are two problems here. First, modifying the policy isn’t sufficient for anything. Second, the policy is either popular or unpopular—there’s no “reduce popularity” condition.

C
We should modify this parking policy if modification will not reduce its popularity with the faculty.

The sufficient condition here is never addressed in the stimulus. The stimulus only considers what happens when the policy is popular or unpopular. There’s no discussion of reductions in popularity.

D
If this parking policy is popular among students, then we should adopt a new policy.

The stimulus states that if the policy is unpopular among students, then we should adopt a new policy. Meanwhile, if the policy is popular as (D) says, we can infer that we should modify the existing policy.

E
If this parking policy is popular with the faculty, then we should adopt a new policy.

If the policy is popular with faculty, then it must be unpopular with students (because it’s bound to be unpopular with at least one group). And if it’s unpopular with students, then we should adopt a new policy.


84 comments

Essayist: Wisdom and intelligence are desirable qualities. However, being intelligent does not imply that one is wise, nor does being wise imply that one is intelligent. In my own experience, the people I meet have one or the other of these qualities but not both.

Summary

Wisdom and intelligence are desirable.

Someone can be intelligent, but not wise.

Someone can be wise, but not intelligent.

In the speaker’s experience, people she meets have either intelligence or wisdom, but not both.

Notable Valid Inferences

Some people do not have both intelligence and wisdom.

A
Most people are neither intelligent nor wise.

Could be true. It’s possible most, or even all people in the world do not have both wisdom and intelligence. None of the facts indicates that there must be someone who has both wisdom and intelligence.

B
Most people are both intelligent and wise.

Could be true. Although (B) would be false if it were limited to the people the stimulus’s author has met, (B) isn’t limited to those people. Most people in the world could be both — the author just hasn’t met them.

C
No one is both wise and intelligent.

Could be true. The stimulus doesn’t say anything indicating that there must be at least one person who is both wise and intelligent. It’s possible nobody has both wisdom and intelligence.

D
No one is either wise or intelligent.

Must be false. The author said she knows people who have one of the qualities of wisdom or intelligence, but not both. That means there’s at least one person out there who has wisdom or intelligence..

E
Many people are intelligent and yet lack wisdom.

Could be true. The author said she knows people who have wisdom or intelligence, but not both. It’s possible many of those people are intelligent, but don’t have wisdom.

This question presumes knowledge of these lessons on Lawgic:
https://classic.7sage.com/lesson/contrapositives-demorgans-law

https://classic.7sage.com/lesson/advanced-negate-some-statements

Don't worry if this question was tough. If you got it right, then you should feel great about yourself!


93 comments

Numismatist: In medieval Spain, most gold coins were minted from gold mined in West Africa, in the area that is now Senegal. The gold mined in this region was the purest known. Its gold content of 92 percent allowed coins to be minted without refining the gold, and indeed coins minted from this source of gold can be recognized because they have that gold content. The mints could refine gold and produced other kinds of coins that had much purer gold content, but the Senegalese gold was never refined.

Summary

A numismatist tells us that most medieval Spanish gold coins were made of gold mined in Senegal. The Senegalese gold was 92 percent pure, which is so pure that it was never refined further before minting the coins. Gold from other sources, however, could be refined and thus still be minted into coins with a gold content higher than the Senegalese gold.

Strongly Supported Conclusions

The strongly supported conclusions that we can find in these facts are:

Most gold coins minted in medieval Spain had a gold content of 92 percent and were made of unrefined gold.

Medieval Spanish mints were able to refine gold from a purity less than 92 percent to a purity above 92 percent.

Some coins were minted in medieval Spain with a gold content higher than 92 percent, and were made of gold that was originally less than 92 percent pure.

A
Coins minted from Senegalese gold all contained the same weight, as well as the same proportion, of gold.

This is not supported. The stimulus never indicates the weight of different coins, only the purity of the gold used to make them. We have no idea whether all coins made from Senegalese gold had the same total weight.

B
The source of some refined gold from which coins were minted was unrefined gold with a gold content of less than 92 percent.

This is strongly supported. We know that 92 percent pure Senegalese gold, the purest known, was never refined, so any refined gold coins had to come from a less-than-92-percent pure source. And the facts state that some more-than-92-percent pure (i.e. refined) coins were made.

C
Two coins could have the same monetary value even though they differed from each other in the percentage of gold they contained.

This is not supported. The facts given don’t suggest anything about the monetary value of different coins, so we just can’t say how that relates to gold percentage.

D
No gold coins were minted that had a gold content of less than 92 percent.

This is not supported. We know that some coins were minted with a gold content of 92 percent and that some were minted with an even higher gold content, but the author never indicates whether or not coins were minted with a lower gold content.

E
The only unrefined gold from which coins could be minted was Senegalese gold.

This is not supported. Just because medieval Spanish mints made coins out of unrefined Senegalese gold, that doesn’t mean they never used other unrefined gold. Maybe they had a source of 90 percent pure gold that they also didn’t refine. We just don’t know!


99 comments

The manager of a nuclear power plant defended the claim that the plant was safe by revealing its rate of injury for current workers: only 3.2 injuries per 200,000 hours of work, a rate less than half the national average for all industrial plants. The manager claimed that, therefore, by the standard of how many injuries occur, the plant was safer than most other plants where the employees could work.

Summarize Argument
The manager concludes that the nuclear plant is safer than most other plants where the plant’s employees could work. As evidence, he cites the fact that the nuclear plant’s rate of injuries is less than half the national average for industrial plants.

Notable Assumptions
The manager assumes that a claim about safety can be derived solely from a statistic about injury rate. This means that he doesn’t believe the magnitude of each individual injury should be factored into any discussion of safety. The manager also assumes that injuries on the job are identified immediately, rather than later in life once employment has finished. It could be that the type of work required at nuclear plants exposes workers to harmful chemicals with latent effects, or that the work is physically demanding.

A
Workers at nuclear power plants are required to receive extra training in safety precautions on their own time and at their own expense.
Whether or not we know if other industrial plants have similar protocols in place, it’s hard to see how this could weaken the manager’s argument. If anything, it makes it possible nuclear power plants really are less dangerous than other plants.
B
Workers at nuclear power plants are required to report to the manager any cases of accidental exposure to radiation.
Like (A), we don’t know if this is true of other industrial plants, too. And like (A), this gives another reason why the manager may well be right about nuclear power plant safety.
C
The exposure of the workers to radiation at nuclear power plants was within levels the government considers safe.
This suggests that nuclear power plant workers aren’t experiencing an additional health risk that other industrial plant workers wouldn’t be exposed to. If anything, this helps the manager’s position.
D
Workers at nuclear power plants have filed only a few lawsuits against the management concerning unsafe working conditions.
It seems nuclear power plant workers don’t find working conditions particularly unsafe. This seems to support the manager’s claim that nuclear plants are relatively safe.
E
Medical problems arising from work at a nuclear power plant are unusual in that they are not likely to appear until after an employee has left employment at the plant.
While nuclear power plants have fewer injuries to report each year, the workers suffer nuclear-plant-unique medical problems once they leave their job at the plant. These problems may outweigh the statistic the manager cites.

77 comments