Doctor: Angiotensinogen is a protein in human blood. Typically, the higher a person’s angiotensinogen levels are, the higher that person’s blood pressure is. Disease X usually causes an increase in angiotensinogen levels. Therefore, disease X must be a cause of high blood pressure.
Summarize Argument: Phenomenon-Hypothesis
The doctor hypothesizes that disease X causes high blood pressure, because it typically increases angiotensinogen levels, which are linked to higher blood pressure.
Identify and Describe Flaw
This is the cookie-cutter flaw of assuming that correlation proves causation. The doctor shows that disease X usually causes higher angiotensinogen levels and that higher angiotensinogen levels are correlated with higher blood pressure. She then jumps to the conclusion that disease X causes high blood pressure. To do this, she must assume that higher angiotensinogen levels actually cause high blood pressure. However, it’s possible that high blood pressure causes higher angiotensinogen levels, or that another factor like smoking or genetics causes both.
A
It confuses a necessary condition for a sufficient condition.
This is the cookie-cutter flaw of confusing necessary and sufficient conditions. The doctor doesn’t make this mistake; her argument relies on causal logic, not conditional logic.
B
It overlooks the possibility that even if a condition causally contributes to a given effect, other factors may fully counteract that effect in the presence of that condition.
The doctor’s argument is flawed because she assumes that angiotensinogen levels cause high blood pressure, not because she overlooks other factors that might counteract the effects of disease X.
C
It illicitly infers, solely on the basis of two phenomena being correlated, that one causally contributes to the other.
In order to conclude that disease X causes high blood pressure by raising angiotensinogen levels, the doctor must assume that high angiotensinogen levels cause high blood pressure. However, her argument only establishes that the two are correlated.
D
It confuses one phenomenon’s causing a second with the second phenomenon’s causing the first.
The only proven causal connection in the argument is that disease X usually causes higher angiotensinogen levels. The doctor doesn’t confuse this by saying that higher angiotensinogen levels cause disease X. Instead, she assumes that they cause high blood pressure.
E
It takes for granted that if one phenomenon often causes a second phenomenon and that second phenomenon often causes a third phenomenon, then the first phenomenon cannot ever be the immediate cause of the third.
This is descriptively inaccurate. The doctor says one phenomenon (disease X) causes a second phenomenon (higher angiotensinogen) and assumes that higher angiotensinogen causes high blood pressure. She then concludes that disease X is the immediate cause of high blood pressure.
A
The ancient mine tapped into a large underground deposit that also supplied nearby riverbeds with significant quantities of gold.
B
The ancient mine may have at one time been operated by the same civilization that was responsible for most of the ancient artifacts.
C
The ancient mine was first operated many centuries before the artifacts were constructed.
D
Ancient gold artifacts were often constructed from gold taken from earlier artifacts.
E
Much of the gold dug from the ancient mine in western Asia was transported to faraway destinations.
Further Explanation
Additional note to (A). With (A) being true, the premises now indicate clearly that the artifact gold originated from the somewhere in the network (large underground deposit) but not any specific node (mine or riverbeds). In fact, knowing that there are additional nodes (riverbeds) reduces the likelihood of the hypothesized node (mine) being the source.
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.
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
B
relies on an ambiguity in the expression “most polluted”
C
does not disclose the basis for the ranking used
D
confuses the state of the individual rivers in the water district with that of the water district as a whole
E
equates a decrease relative to the other ranked rivers with an absolute decrease
A
The family members of the organizer of the contest were not permitted to participate in the contest.
B
The manner in which the contest winner would be selected was publicized prior to the selection of the winner.
C
The contest entry forms were submitted at a consistent rate throughout the registration period.
D
The rules of the contest were posted conspicuously by those who organized the contest.
E
The number of people entering the contest far exceeded the expectations of the contest organizers.
A
Cuttlefish feed primarily on small fish and mollusks.
B
Groups of small fish are likely to attract a cuttlefish’s predators.
C
Small fish are more easily scared off by a startle display than are a cuttlefish’s predators.
D
Cuttlefish have acute senses and are able to change colors.
E
Unlike insects that use startle displays, cuttlefish are usually able to move faster than their predators.