Summarize Argument
The author concludes that the supplier’s rate of defects for items it manufactures is not below 5 percent, as the contract requires. This is based on the fact that after testing samples of products sent by field inspectors from various manufacturing locations, the lab found that over 20% of the samples were defective.
Identify and Describe Flaw
The author assumes that the rate of defect in the samples sent by field inspectors is representative of the rate of defect in the overall set of products manufactured by the supplier. This overlooks the possibility that the samples selected have a higher rate of defect than the average product (perhaps because the field inspectors might be looking for potentially defective items).
A
bases its conclusion on too small a sample of items tested by the laboratory
We have no reason to think the sample of items sent by the inspectors is too small. In order to pick (A), we need some textual hook in the stimulus to suggest the sample size is too small.
B
presumes, without providing justification, that the field inspectors were just as likely to choose a defective item for testing as they were to choose a nondefective item
The assumption is that rate of choosing defects did not exceed the actual defect rate. (Ex. Actual rate is 25% defects, and inspectors chose defective items 25% of the time, nondefect 75%.) This doesn’t require chance of choosing defect to be equal to choosing nondefect (50-50).
C
overlooks the possibility that a few of the manufacturing sites are responsible for most of the defective items
This doesn’t undermine the argument, because we have no reason to think that a few sites being responsible for most defects would skew the defect rate in the inspectors’ sample. We have no reason to think the inspectors disproportionately picked items from these few sites.
D
overlooks the possibility that the field inspectors tend to choose items for testing that they suspect are defective
This undermines the argument, because it shows that the sample selected by inspectors might have a higher rate of defect than the average product produced by the supplier. This is why we can’t assume the over 20% defect rate in the sample applies to the overall set of products.
E
presumes, without providing justification, that the field inspectors made an equal number of visits to each of the various manufacturing sites of the supplier
The author does assume that the manner in which the inspectors collected items for the sample was not biased in a way that made the defect rate in the sample unrepresentative of the overall defect rate, but this doesn’t require any view about the number of visits.
Summarize Argument
The essayist concludes that microorganisms brought to North America by prehistoric humans caused many species of native animals to go extinct within the next 2,000 years. This is because the prehistoric humans wouldn’t have been able to hunt those animals to extinction, and those same humans certainly brought microorganisms with them.
Notable Assumptions
Based on the fact that humans couldn’t have hunted the animals to extinction, the essayist concludes that it must’ve been microorganisms. This means the essayist doesn’t believe there’s any other means besides humans and microorganisms that could’ve caused the animals to go extinct. The essayist also believes that there was nothing common to the animals that went extinct that wasn’t common to those that didn’t go extinct—for example, perhaps those animals were sensitive to climate changes around that time.
A
Animals weakened by disease are not only less able to avoid hunters but are also less able to avoid their other predators.
This seems to strengthen the essayist’s argument. The diseased animals were susceptible to hunters and predators alike, giving yet another reason why they died out.
B
Human beings generally have a substantial degree of biological immunity to the diseases carried by other species.
We don’t care about the diseases humans are susceptible to. We need to know about the animals that went extinct.
C
Very few species of North American animals not hunted by the new arrivals from Asia were extinct 2,000 years after the first migrations.
Hunting by humans indeed made a difference. The vast majority of the species that went extinct were hunted, which provides us with an alternate hypothesis for how those animals went extinct.
D
Individual humans and animals can carry a disease-causing microorganism without themselves suffering from the disease.
Perhaps the animals that died out were ones that couldn’t carry the microorganisms without suffering from disease. We don’t know.
E
Some species of North American animals became extinct more than 2,000 years after the arrival in North America of the first prehistoric human migrants from Asia.
We care about the animals that became extinct within 2,000 years.
Summarize Argument: Phenomenon-Hypothesis
The author hypothesizes that nutritious breakfasts makes workers more productive. This is based on a study in which workers at one plant received free nutritious breakfasts every day before work, and workers at another plant did not get free nutritious breakfasts every day before work. After one month, the productivity of the first plant’s workers increased, while that of the second plant’s workers did not.
Notable Assumptions
The author assumes that nutritious breakfasts caused the increased productivity in th first plant. The author also assumes that workers in the second plant did not eat nutritious breakfasts. (This overlooks the possibility that, even though they didn’t get free nutritious breakfasts, they still could have eaten breakfasts on their own.)
A
Few workers in Plant B consumed nutritious breakfasts during the month of the study.
This strengthens by helping to establish that the second plants’s workers generally did not eat nutritious breakfasts during the study. If this were not true, then both groups would have had nutritious breakfasts and there would have been no control group.
B
Workers in the study from Plant A and Plant B started work at the same time of day.
It’s not clear that having the same start time strengthens the argument, becaue having different start times would not necessarily weaken the argument.
C
During the month before the study, workers at Plant A and Plant B were equally productive.
The study observed that Plant A’s productivity increased, and Plant B’s productivity didn’t increase. Starting productivity point doesn’t matter, because we’re only comparing increase vs. no increase. We’re not comparing one’s plant’s productivity to another’s.
D
Workers from Plant A took fewer vacation days per capita during the month than did workers from Plant B.
Plant A’s productivity increased, while Plant B’s did not. We’re not comparing one plant’s productivity to the other’s; we’re just comparing the presence of an increase to the lack of an increase. So, comparative vacation days don’t affect the argument.
E
Workers in Plant B were more productive during the month of the study than were workers from Plant A.
The study observed that Plant A’s productivity increased, and Plant B’s productivity didn’t increase. We’re not comparing one plant’s productivity to another’s.