Many people joke about Friday the thirteenth being an unlucky day, but a study showed that in one year approximately 17 percent of people scheduled to fly canceled or did not show up for their flights on Friday the thirteenth—a rate higher than that on any other day and date in that year. This shows that a significant percentage of the population would rather disrupt their travel plans than risk flying on a supposedly unlucky day.

Summarize Argument: Phenomenon-Hypothesis
The author hypothesizes that a significant proportion of the population are willing to disrupt their plans to avoid flying on an “unlucky” Friday the thirteenth. This hypothesis is based on the observation that during a particular year, more people cancelled or didn’t show up to their flights on Friday the thirteenth than on any other day that year.

Notable Assumptions
The author assumes that the reason people didn’t show up for their flights on Friday the thirteenth was the unlucky date, and not some other reason. There aren’t that many Fridays the thirteenth in a single year, so maybe some other significant factor just happened to arise on one or more Fridays the thirteenth that year.

A
People who fly tend to be professionals who as a group are less superstitious than the general public.
This does not weaken the argument. Even if people who fly are less superstitious, that doesn’t mean they’re not superstitious at all—maybe it’s just that even more of the general public would have skipped their flights. This still doesn’t explain the observed phenomenon.
B
Surveys show that less than 5 percent of the population report that they believe that Friday the thirteenth is an unlucky day.
This does not weaken the argument. Firstly, this is just trying to undermine the premise that people skip their flights more often on Friday the thirteenth. Secondly, it doesn’t succeed: someone might claim not to be superstitious but still not want to fly on an “unlucky” day.
C
Weather conditions at several major airports were severe on the Fridays that fell on the thirteenth in the year of the study.
This weakens the argument by providing an alternative explanation for why more people missed their flights on Friday the thirteenth. If there happened to be severe weather those days, it makes sense that people would miss their flights even without superstition being involved.
D
In the year of the study, automobile traffic was no lighter on Friday the thirteenth than on other Fridays.
This does not weaken the argument, because the domain of the argument is specific to flights. It would be perfectly reasonable for people to fear flying on an unlucky day but not fear driving, because driving is a much more routine activity.
E
The absentee rate among airline workers was not significantly higher than normal on the Fridays that fell on the thirteenth in the year of the study.
This does not weaken the argument, because there are other factors that explain why airline workers might show up to work on an “unlucky” day. So this doesn’t really contradict the observed data about passengers, and still doesn’t explain the phenomenon.

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Astronomer: Mount Shalko is the perfect site for the proposed astronomical observatory. The summit would accommodate the complex as currently designed, with some room left for expansion. There are no large cities near the mountain, so neither smog nor artificial light interferes with atmospheric transparency. Critics claim that Mount Shalko is a unique ecological site, but the observatory need not be a threat to endemic life-forms. In fact, since it would preclude recreational use of the mountain, it should be their salvation. It is estimated that 200,000 recreational users visit the mountain every year, posing a threat to the wildlife.

Summarize Argument
The astronomer claims that Mount Shalko is a perfect site for a new proposed observatory. The support follows two lines of reasoning.
First, the site is suitable. There’s enough space for the building and no smog or light pollution from nearby cities.
Second, it would protect ecology, not harm it as some critics fear. The mountain currently has many recreational users who threaten its ecology, but recreational use would be precluded by the observatory.

Notable Assumptions
The astronomer assumes that the site would remain suitable, for example that no new cities are planned to be built nearby in the near future.
The astronomer also assumes that the process of building the observatory, and the building’s ongoing presence on the mountain, wouldn’t harm the mountain’s ecology more than the current recreational use does.

A
More than a dozen insect and plant species endemic to Mount Shalko are found nowhere else on earth.
This does not weaken the argument, because the astronomer never contests the point that Mount Shalko is a unique ecological site. Instead, the argument is that the observatory would actually protect the mountain’s ecology by precluding recreational use.
B
A coalition of 14 different groups, as diverse as taxpayer organizations and hunting associations, opposes the building of the new observatory.
This does not weaken the argument, because the number or type of people who oppose building the observatory has no bearing on the astronomer’s argument. Just because there’s broad opposition, that tells us nothing about the merits of the astronomer’s claims.
C
Having a complex that covers most of the summit, as well as having the necessary security fences and access road on the mountain, could involve just as much ecological disruption as does the current level of recreational use.
This weakens the argument by undermining the astronomer’s claim that the observatory would protect the mountain’s ecology by eliminating recreational use. If the observatory could be just as harmful, then there’s no ecological benefit to building it.
D
The building of the observatory would not cause the small towns near Mount Shalko eventually to develop into a large city, complete with smog, bright lights, and an influx of recreation seekers.
This does not weaken the argument, because it partially affirms the astronomer’s assumption that no new cities will soon develop near Mount Shalko. In fact, by doing so, this strengthens the argument.
E
A survey conducted by a team of park rangers concluded that two other mountains in the same general area have more potential for recreational use than Mount Shalko.
This does not weaken the argument because whether or not other nearby mountains are suitable for recreational use is irrelevant. Mount Shalko is already used for recreation, and the observatory would stop that use. This doesn’t change any of that.

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Two hundred randomly selected subjects were asked, “Have you ever awakened, seemingly paralyzed, with a sense of a strange presence in the room?” Forty percent answered yes. A randomly selected control group of 200 different subjects in the same study were asked simply if they remembered ever waking up seemingly paralyzed. Only 14 percent of the control group answered yes.

Summary
There were two groups in a study. The first group was asked if they had ever awakened feeling paralyzed with the sense of a strange presence, with 40% answering yes. The other group was asked if they had ever woken up seemingly paralyzed, with only 13% answering yes.

Strongly Supported Conclusions
The way a question is asked/framed can impact the responses.
The broader a question is, the more people are likely to relate to it.

A
Experiencing a sense of a strange presence in a room in some way causes subjects to feel as though they are paralyzed.
There is no causal link between sensing a strange presence and feeling paralyzed. It is more likely that the mention of a strange presence broadened the relatability of the statement.
B
The number of subjects who had awakened with a sense of a strange presence in the room was greater in the first group than in the control group.
This is not supported. The second group was not asked about a strange presence.
C
If the reports of the first group of subjects were accurate, approximately 60 percent of them had never awakened with a sense of a strange presence in the room.
This is too strong to support. The way the question was asked to the first group implies that they could answer “yes” to feeling paralyzed OR sensing a strange presence. Thus, it is unclear what percentage has/has not *just* felt a strange presence.
D
At least some of the randomly selected subjects of the study gave inconsistent reports.
There is no indication that any subjects gave inconsistent reports. The inconsistency in the study is *between* the two groups, not within them.
E
The tendency of subjects to report a recollection of an event can sometimes be increased by suggesting circumstances that accompanied the event.
The difference between the two groups could be caused by the fact that the first group had a broader question. Thus, the tendency to report a recollection of an event (paralyzed) can be increased (14% vs 40%) by suggesting additional circumstances (sensing a strange presence).

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Very powerful volcanic eruptions send large amounts of ash high into the atmosphere, blocking sunlight and causing abnormally cold temperatures for a year or more after the eruption. In 44 B.C. there was a powerful eruption of Mount Etna in Sicily. In the following year, Chinese historians recorded summer frosts and dimmed sunlight in China, thousands of miles east of Sicily. If these phenomena were caused by volcanic ash in the atmosphere, then the ash sent into the atmosphere by Mount Etna’s eruption must have spread over great distances.

Summarize Argument
The author concludes that if volcanic ash caused dimmed sunlight and cool summers in China in 43 B.C., then the ash caused by Mount Etna must’ve spread over vast distances. This is because Mount Etna erupted in 44 B.C., and powerful volcanoes can cause such phenomena.

Notable Assumptions
The author assumes that if a volcano caused the phenomena in China, then that volcano was Mount Etna. This means the author assumes there were no other volcanos powerful enough to cause such phenomena in 44-43 B.C.

A
modern monitoring equipment can detect the precise path of volcanic ash in the atmosphere
This eruption was in 44 B.C. We don’t care if modern monitoring equipment can track volcanoes today.
B
the abnormal weather in China lasted for a full year or longer
We know powerful volcanoes can cause effects that last a year or longer. But that doesn’t mean those effects have to last a year or longer in order to associate them with a powerful volcanic eruption.
C
temperatures in Sicily were abnormally cold after Mount Etna erupted
Knowing the answer to this wouldn’t strengthen or weaken the author’s argument, which is that Mount Etna caused the phenomena in China. We don’t care about conditions in Sicily.
D
there were any volcanic eruptions near China around the time of Mount Etna’s eruption
If the answer is yes, then we have viable alternate explanation to the author’s: other volcanoes, rather than Mount Etna, caused cool summers and dimmed sunlight. If the answer is no, then it would seem Mount Etna was the volcano most likely to have caused such phenomena.
E
subsequent eruptions of Mount Etna were as powerful as the one in 44 B.C.
We’re not interested in subsequent eruptions. Knowing the answer wouldn’t tell us whether the 44 B.C. eruption likely caused the phenomena in China.

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