A certain medication that is frequently prescribed to lower a patient’s cholesterol level is generally effective. A recent study of 1,000 subjects ranging widely in age indicates, however, that the cholesterol level of someone taking the medication is typically 12 to 15 percent higher than the average for that person’s age group.

"Surprising" Phenomenon
Why would the cholesterol of someone taking the medication be typically higher than the average cholesterol of someone in that person’s age group even though the medication is effective in lowering cholesterol?

Objective
The correct answer should tell us about a difference between people who take the medication and people who don’t that might explain why people who take the medication have higher average cholesterol despite the medication’s effectiveness. For example, maybe people who take the medication start off with above average cholesterol, which could be why the take the medication in the first place. Or maybe people who take the medication engage in cholesterol-increasing activities that the average person does not.

A
A recently developed cholesterol-lowering medication is more effective than the medication described above.
A new, different drug has no impact if we have no reason to think that the average person takes that new drug.
B
Another medication is prescribed to treat high cholesterol just as often as the medication described above is.
A different drug has no impact if we have no reason to think that the average person takes that new drug. Even if we did know that the average person takes a different drug, we don’t know that the different drug is more effective at decreasing cholesterol.
C
In most cases, people with high cholesterol levels are not treated with drug therapy but are put on restrictive low-cholesterol diets.
What happens to most people with high cholesterol doesn’t matter, because we’re trying to explain a discrepancy concerning people who are on the cholesterol-reducing drug.
D
The medication described above is usually prescribed only for people whose cholesterol level is at least 30 percent above the average for their age group.
This tells us people given the medication typically start with cholesterol significantly higher than average. That’s why the drug, even though it helps reduce cholesterol, does not bring the drug-takers’ cholesterol level down to the average person’s cholesterol level.
E
Within the population as a whole, approximately the same number of people have relatively high cholesterol levels as have relatively low cholesterol levels.
The specific number of people with high or low cholesterol does not affect average cholesterol levels of people who take the medication or average cholesterol levels of people who don’t take the medication.

3 comments

It is easy to see that the board of directors of the construction company is full of corruption and should be replaced. There are many instances of bribery by various persons on the staff of board member Wagston that are a matter of public record. These bribes perniciously influenced the awarding of government contracts.

Summarize Argument
The author concludes that every person on the company’s board of directors is corrupt and should be replaced. This is because one of the board members, Wagston, has people on his staff who engaged in bribery.

Identify and Describe Flaw
The problem with this argument is that it claims that the entire board of directors should be replaced even though the incriminating evidence only implicates certain members of Wagston’s staff. There may be some support for the claim that those staff members are corrupt, but the argument never establishes that even Wagston himself is, let alone the entire board.

A
the argument fails to show that corruption is not limited to Wagston’s staff
This describes how the argument only offers evidence that certain staff members are corrupt, yet concludes that the entire board of directors should be replaced. There’s no evidence that anyone on the board was corrupt.
B
the argument fails to show that Wagston’s staff engaged in any bribery other than bribery of government officials
This is irrelevant. Whether the staff committed other kinds of bribery or not, there still wouldn’t be evidence that all of the board members are corrupt.
C
the argument fails to specify the relation between bribery and corruption
The argument doesn’t fail to specify this relation since it says that the bribes perniciously influenced the awarding of contracts. The issue is that this still doesn’t implicate the board members.
D
the argument presumes without giving justification that all of Wagston’s staff have engaged in corruption
The argument doesn’t do this since it only says “various persons on the staff” engaged in bribery. Whether the entire staff engaged in corruption or not, there’s no evidence that their actions implicate the board members.
E
the argument attempts to deflect attention away from substantive issues by attacking the character of the board
The author is accusing the board members of corruption, so the character of the board is itself a substantive issue for the argument.

24 comments

Climatologists believe they know why Earth has undergone a regular sequence of ice ages beginning around 800,000 years ago. Calculations show that Earth’s orbit around the Sun has fluctuations that coincide with the ice-age cycles. The climatologists hypothesize that when the fluctuations occur, Earth passes through clouds of cosmic dust that enters the atmosphere; the cosmic dust thereby dims the Sun, resulting in an ice age. They concede, however, that though cosmic dust clouds are common, the clouds would have to be particularly dense in order to have this effect.

Summarize Argument: Phenomenon-Hypothesis
The author hypothesizes that the regular sequence of ice ages Earth has experienced since 800,000 years ago are caused by Earth’s passing through clouds of cosmic dust. According to this theory, the cosmic dust enters Earth’s atmosphere, which dims the sun, causing an ice age.

Notable Assumptions
The author assumes there’s no other explanation for what causes Earth’s regular sequence of ice ages. The author assumes that the occurrence of ice ages is correlated with Earth’s passage through clouds of cosmic dust.

A
Earth did not pass through clouds of cosmic dust earlier than 800,000 years ago.
This strengthens by defending the argument from the possibility that passage through cosmic dust occcurred before the ice ages starting to occur.
B
Two large asteroids collided 800,000 years ago, producing a tremendous amount of dense cosmic dust that continues to orbit the Sun.
This helps establish that the dense cosmic dust the author’s hypothesis requires actually exists and correlates with the beginning of the ice ages.
C
Earth’s average temperature drops slightly shortly after volcanic eruptions spew large amounts of dust into Earth’s atmosphere.
This strengthens by showing that dust in Earth’s atmosphere can reduce Earth’s average temperature. This makes the author’s theory about dust causing ice ages more plausible. Although (C) is about volcanic dust, it still shows that dust in atmosphere can cool the Earth.
D
Large bits of cosmic rock periodically enter Earth’s atmosphere, raising large amounts of dust from Earth’s surface.
(D) tells us that cosmic rock periodically enters the atmosphere. But does the Earth get colder after this happens? We don’t know. Do these periodic entries of cosmic rock coincide with Earth’s ice ages? We don’t know. (D) has no impact.
E
Rare trace elements known to be prevalent in cosmic debris have been discovered in layers of sediment whose ages correspond very closely to the occurrence of ice ages.
This provides evidence of a correlation between cosmic debris and the occurrence of ice ages.

65 comments