Shelton: The recent sharp decline in the number of moose in this region was caused by a large increase in the white-tailed deer population. While the deer do not compete with moose for food, they carry a dangerous parasite that can be transferred to any moose living nearby.

Russo: The neighboring region has also experienced a large increase in the white-tailed deer population, but the moose population there has remained stable.

"Surprising" Phenomenon

An increase in white-tailed deer caused a corresponding decline in moose in one region, whereas similar conditions didn’t produce the same phenomenon in the neighboring region.

Objective

The right answer will be a hypothesis that explains a key difference between the two regions in question. That difference must likely result in the first region being more susceptible to parasite transfer from deer to moose, or in the neighboring region being less susceptible to parasite transfer.

A
The region with the declining moose population is larger than the neighboring region and, even after the decline, has more moose than the neighboring region.

We already know that the first region’s moose declined. This doesn’t explain why the neighboring region’s moose didn’t experience a decline, too.

B
The region with the declining moose population consists mainly of high-quality moose habitat, but the quality of moose habitat in the neighboring region is marginal.

How would poorer-quality habitat help the moose in the neighboring region? We need to know why the neighboring population didn’t suffer the same problems after an increase in white-tailed deer.

C
Wolf packs in the region with the declining moose population generally prey on only moose and deer, but in the neighboring region the wolf packs prey on a wider variety of species.

For this to work, we would need to know how many moose and deer are being killed relative to one another, as well as how those numbers compare across the regions. We don’t have enough information for this to resolve the conflict.

D
There is a large overlap in the ranges of moose and white-tailed deer in the region with the declining moose population, but not in the neighboring region.

In the region where moose are declining, the parasite transfer is actually occurring. In the neighboring region, moose and deer live in separate areas and thus rarely interact. This explains why the moose in the neighboring region aren’t being infected.

E
Moose require a habitat with very little human settlement, whereas white-tailed deer often thrive in and around areas with considerable human settlement.

We have no idea if either region has human settlement.


29 comments

Last year the Lalolah River was ranked by the Sunvale Water Commission as the most polluted of the fifteen rivers in the Sunvale Water District. Measures taken to clean up the river must be working, though, since this year the Lalolah River is ranked as only the third most polluted river in the district.

Summarize Argument: Phenomenon-Hypothesis
The author hypothesizes that the efforts to clean the Lalolah River are working. He supports this by saying that the river was ranked the third most polluted this year, while it was ranked the most polluted last year.

Identify and Describe Flaw
This is the flaw of confusing relative and absolute change. The author shows that the Lalolah River is less polluted this year than the top two most polluted rivers, and then assumes that it’s cleaner than it was last year. But just because the Lalolah River is less polluted than other rivers doesn’t mean that it’s actually gotten less polluted.

The other rivers might have just gotten much dirtier, while the Lalolah River stayed the same. If so, the author can’t conclude that the cleanup efforts are working.

A
interprets lack of evidence for a claim as support for an opposing claim
This is the cookie-cutter flaw of assuming that an opponent’s conclusion is false, simply because their argument lacks evidence. The author doesn’t make this mistake; he isn’t countering someone else’s position or supporting an opposing claim at all.
B
relies on an ambiguity in the expression “most polluted”
This is the cookie-cutter flaw of equivocation, where the argument uses the same term in different ways. The author doesn’t make this mistake. He may not explain the exact meaning of “most polluted,” but he does use the term clearly and consistently throughout his argument.
C
does not disclose the basis for the ranking used
The author doesn’t need to explain how the pollution rankings are determined. Even if he did, his argument would still be flawed because he confuses the river being cleaner than other rivers with it being cleaner overall.
D
confuses the state of the individual rivers in the water district with that of the water district as a whole
The author never makes any claims about the state of the water district as a whole. Instead, he confuses the state of the Lalolah River compared to other rivers with the state of the Lalolah River this year compared to last year.
E
equates a decrease relative to the other ranked rivers with an absolute decrease
Just because the Lalolah River is less polluted than two other rivers does not mean that it’s less polluted than it was last year. Maybe the other rivers just got dirtier.

7 comments

If the winner of a promotional contest is selected by a lottery, the lottery must be fair, giving all entrants an equal chance of winning. Since 90 percent of the winners selected by the lottery in a recent promotional contest submitted their entry forms within the first 2 days of the 30-day registration period, it is clear that this lottery did not meet the fairness requirement.

Summarize Argument
The author concludes the lottery didn’t give all entrants an equal chance of winning. Why not? Because 90 percent of the people who won had entered within the first 2 days of the registration period, which was 30 days long.

Notable Assumptions
The author assumes the lottery gave early entrants a more-than-even chance of winning, and that’s why most people who won had entered early. In particular, this means assuming that significantly fewer than 90 percent of the total entries were submitted within the first 2 days.

A
The family members of the organizer of the contest were not permitted to participate in the contest.
This is irrelevant. It makes no claim about the timing of lottery entries or the selection process. If anything, it suggests the lottery is more likely to have been fair, not less.
B
The manner in which the contest winner would be selected was publicized prior to the selection of the winner.
This is irrelevant. It doesn’t say that method gave any early entrants a higher chance of winning.
C
The contest entry forms were submitted at a consistent rate throughout the registration period.
This makes concrete the author’s primary assumption: that fewer than 90 percent of the total entries were submitted in the first two days. It makes it less likely that pure chance caused most of the winners to be early entrants.
D
The rules of the contest were posted conspicuously by those who organized the contest.
This is irrelevant. It doesn’t say those rules gave early entrants a better chance of winning than late entrants.
E
The number of people entering the contest far exceeded the expectations of the contest organizers.
This is irrelevant. It doesn’t imply the lottery organizers selected winners before the contest ended, or that they gave early entrants a better chance of winning.

23 comments

When researchers discovered that cuttlefish have the ability to make themselves suddenly appear larger, they presumed that this behavior, called a “startle display,” was used to scare off predators. A long-term study, however, reveals that cuttlefish never use startle displays to scare off predators but instead only use such displays to scare off small fish that do not prey on cuttlefish.

"Surprising" Phenomenon
Cuttlefish use their startle display to scare off harmless fish rather than predators.

Objective
The correct answer will be a hypothesis that explains why cuttlefish use startle displays. That explanation must result in cuttlefish gaining some benefit from using their startle display with small, harmless fish, but gaining either no benefit or a negligible benefit from using their startle display with predators.

A
Cuttlefish feed primarily on small fish and mollusks.
Cuttlefish use their startle displays on small fish. Why would cuttlefish want to scare off their prey?
B
Groups of small fish are likely to attract a cuttlefish’s predators.
Cuttlefish use their startle displays on small fish to pre-emptively avoid their predators. Small fish attract predators, so it makes sense cuttlefish would want to scare them away.
C
Small fish are more easily scared off by a startle display than are a cuttlefish’s predators.
This doesn’t explain why cuttlefish would bother scaring off small fish in the first place.
D
Cuttlefish have acute senses and are able to change colors.
Like (C), this doesn’t explain the why cuttlefish bother scaring off small fish. We don’t care about their other abilities.
E
Unlike insects that use startle displays, cuttlefish are usually able to move faster than their predators.
This explains why cuttlefish don’t use startle displays with predators. But why do they bother using them with small fish?

8 comments

A store was vandalized repeatedly over a six-month period. When discussing the problem with a friend, the store owner mentioned having heard that bright lighting around the perimeter of commercial establishments had been known to reduce the incidence of vandalism. Three months later, the store owner reported to the same friend that there had been no incidents of vandalism since their previous conversation. The friend concluded that bright lighting had been installed around the perimeter of the store.

Summarize Argument: Phenomenon-Hypothesis
The friend hypothesized that bright lighting had been installed around the perimeter of the store. This is based on the fact that the store owner had mentioned to the friend that bright lighting has been known to reduce the rate of vandalism, and three months after that conversation, the rate of vandalism at the store owner’s store had dropped to zero.

Notable Assumptions
The friend assumes that there’s no other explanation for why the rate of vandalism dropped besides the installation of bright lighting around the perimeter. The friend also assumed that it was possible for the store owner to install bright lighting around the perimeter.

A
There had been an increase in police patrolling of the area.
This provides an alternate explanation for the drop in vandalism.
B
Bright lights must be specially ordered from a security company, and installation by the company usually takes at least five months.
Since the report of a drop in vandalism occurred only three months after the initial conversation, (B) provides a reason to think the store owner wouldn’t have been able to install bright lighting yet.
C
The store owner reported that all the stores adjacent to the perimeter also experienced a reduction in vandalism, although stores one block away did not.
This provides evidence that could support the theory that bright lights had been installed. Stores near those lights also experienced a drop in vandalism, but stores that were not near those lights did not experience a drop.
D
The store’s budget did not allow for the installation of bright lights around the perimeter.
This provides a reason to think the store owner would not have been able to install bright lights around the perimeter.
E
The store owner brought in a watchdog to protect the store from vandals.
This provides an alternate explanation for the drop in vandalism.

15 comments

Requiring that passwords conform to rules of length, complexity, and unpredictability increases the likelihood of someone gaining unauthorized access to a user’s account. Since most user accounts are automatically locked after a certain number of incorrect password guesses, it is usually impossible to gain access by guessing a password. However, because complex passwords can be hard to remember, users often write them down.

Summarize Argument
The author concludes that making people use long, complex, unpredictable passwords actually increases the chances their accounts are hacked. Why? Because it’s hard to access an account by guessing a password anyway, and complex passwords are more difficult to remember, meaning people usually write them down.

Notable Assumptions
The author assumes the risk of a written password being stolen is greater than the risk of a non-complex password being guessed. This means assuming people are more likely to write down a complex password, and that writing down a password increases the chances a person’s account is accessed without authorization.

A
People who use mnemonic devices to help remember their passwords are able to easily remember passwords that are long, complex, and unpredictable.
This doesn’t change the fact that people often write down complex passwords. It offers a method people can use to avoid writing their passwords down, but it doesn’t say that method is widespread.
B
User accounts that are automatically locked after a certain number of incorrect password guesses are usually unlocked after a reasonable time.
This doesn’t mean passwords are easy to guess. It doesn’t say a locked account is unlocked quickly enough to allow passwords to be at risk from repeated guessing.
C
When a password is written down, it increases the chances that someone will be able to use that password to gain unauthorized access to the user’s account.
This makes concrete the author’s assumption that a person’s account is more likely to be accessed without authorization if they write their password down. It confirms that the stated disadvantage of complex passwords—people tend to write them down—really is a disadvantage.
D
When users who forget their passwords are locked out of their own accounts, they must often go through a complicated process in order to have their accounts unlocked.
This is irrelevant. It implies users are motivated to remember their passwords, but it doesn’t say users are more likely to write down complex passwords than non-complex passwords.
E
Passwords that conform to rules of length, complexity, and unpredictability are no harder to guess than passwords that do not conform to such rules.
This doesn’t affect the argument. The author says it’s hard to access an account by guessing a password—complex or not. This isn’t an additional disadvantage of complex passwords.

6 comments

Anderson: Taking the long view, history shows that word usage and grammar rules are constantly changing and evolving—sometimes resulting in entirely new languages. Since they will change regardless of our efforts, we shouldn’t worry about violations of grammar rules.

Lipton: That’s like arguing that we shouldn’t worry about enforcing laws since, in the larger scheme of things, laws change and nations come and go. But of course it is good that laws are enforced.

Speaker 1 Summary
Anderson says that we shouldn’t worry about enforcing grammar rules. In support, Anderson says that these rules will change over time anyway. And how do we know this? Because history shows that grammar rules are always changing.

Speaker 2 Summary
Lipton’s argument leads to the unstated conclusion that we should enforce grammar rules. Lipton supports this by drawing an analogy between grammar rules and laws, since both change over time. However, Lipton says, it’s good to enforce laws—implying that it’s also good to enforce grammar rules.

Objective
We want to find a disagreement between Anderson and Lipton. The two disagree about whether we should enforce grammar rules.

A
grammar violations should be resisted
Anderson disagrees with this and Lipton agrees, so this is the disagreement. Anderson’s main conclusion is that we shouldn’t enforce grammar rules—put differently, we shouldn’t resist grammar violations. Lipton’s implied conclusion is the opposite, that we should resist.
B
a language can evolve into an entirely new language
Anderson agrees with this, and most likely, Lipton does as well. Lipton seems to take Anderson’s claims about language evolution for granted, and just disagrees about whether that’s a basis to ignore grammar rules.
C
users of a language can easily adapt to changes in that language
Neither speaker makes this claim. Anderson is the only one who talks directly about how languages change over time, but even so doesn’t mention how users of the language are impacted by those changes.
D
people only rarely violate grammar rules
Neither speaker expresses an opinion about this claim. Anderson and Lipton are discussing in the abstract whether grammar rules should be enforced. Neither one mentions how often people actually violate those rules.
E
languages evolve through an accumulation of changes in usage and rules
Anderson most likely agrees with this, and Lipton probably does as well. Anderson’s description of language evolution (which Lipton seems to accept) does mention that changes in usage and rules can cause new languages. That’s consistent with this statement.

2 comments

Student: My university recently enacted new penalties for drinking alcohol in on-campus student housing. But the university has attempted to curb on-campus drinking many times in the past, and these attempts have never been successful. Thus, these new penalties are bound to be just as ineffective.

Summarize Argument

The student concludes that the new penalties for on-campus drinking will be ineffective. He supports this by saying that past attempts to curb on-campus drinking were ineffective.

Identify and Describe Flaw

The student draws an analogy between the new efforts to stop on-campus drinking and the past efforts, claiming the new efforts will be just as ineffective. He assumes that the new and past efforts are relevantly similar, ignoring the possibility that there may be important differences that could make the new efforts more successful.

A
fails to specify what new penalties the university enacted for drinking alcohol in on-campus student housing

The student doesn’t need to explain what the new penalties are. Instead, he needs to explain why they’ll be ineffective. Even if he did specify them, his argument would still be flawed because he assumes the new penalties will fail simply because past efforts did.

B
overlooks the possibility that many students did not drink alcohol in on-campus student housing even before the new penalties were enacted

The student doesn’t overlook this possibility. Many students at the university may not drink at all; the penalties only target those students who do drink in on-campus housing.

C
presumes, without providing justification, that students’ preferred location for drinking alcohol is on-campus student housing

The student doesn’t assume that students prefer to drink on campus, just that some students do drink on campus. Whether students prefer to drink elsewhere is irrelevant; the penalties only target on-campus drinking.

D
overlooks the possibility that the new penalties are relevantly different from the university’s past attempts to curb on-campus drinking

The student assumes that the new penalties are relevantly similar to the university’s past attempts to curb on-campus drinking. If they’re relevantly different, he can’t conclude that the new ones will be ineffective simply because the old ones were.

E
fails to consider whether the new penalties will have any other positive consequences besides reducing drinking in on-campus student housing

It doesn't matter whether the new penalties have other positive consequences. The student only addresses whether these penalties will effectively reduce drinking in on-campus housing.


3 comments