Summarize Argument
The author concludes that it’s likely Tom is an extreme insomniac. This is based on the fact that 90 percent of extreme insomniacs drink lots of coffee, and Tom drinks lots of coffee.
Identify and Describe Flaw
The author misinterprets the claim “Most A are B” as “Most B are A.” Although 90 percent of extreme insomniacs drink lots of coffee, that doesn’t tell us anything about what proportion of lots-of-coffee drinkers are extreme insomniacs. It could be that the vast majority of lots-of-coffee drinkers aren’t extreme insomniacs, even if most extreme insomniacs drink lots of coffee.
A
It fails to acknowledge the possibility that Tom is among the 10 percent of people who drink large amounts of coffee who are not extreme insomniacs.
The premises don’t establish that only 10 percent of people who drink lots of coffee are not extreme insomniacs. Also, the conclusion doesn’t say that Tom definitely is an extreme insomniac. So, the author acknowledges that he might not be an extreme insomniac.
B
It fails to consider the possible contribution to extreme insomnia of other causes of insomnia besides coffee.
The author’s argument does not make any assumptions about cause. The issue is whether membership in the set of people who drink lots of coffee implies a likelihood of membership in the set of people who are extreme insomniacs.
C
It relies on evidence that does not indicate the frequency of extreme insomnia among people who drink large amounts of coffee.
The author relies on the fact that 90% of extreme insomniacs drink lots of coffee. This does not reveal the frequency (i.e. proportion) of extreme insomnia among people who drink lots of coffee. It could be that only a small % of lots-of-coffee drinkers have extreme insomnia.
D
It draws an inference about one specific individual from evidence that describes only the characteristics of a class of individuals.
The author does not commit the whole-to-part fallacy. The issue is misinterpretation of the claim “90% of extreme insomniacs consume lots of coffee.” This statistic is not a claim about a class — it’s a claim about 90% of the individuals within the class.
E
It presumes without warrant that drinking coffee always causes insomnia.
The author doesn’t make any assumptions about cause. The issue is whether membership in the set of people who drink lots of coffee implies a likelihood of membership in the set of people who are extreme insomniacs.
Summarize Argument
The author concludes that the Acme retirement plan is probably a good plan for anyone with retirement needs similar to the Economic Merit Prize winners. This is based on the fact that each of the winners from the past 25 years is covered by the Acme retirement plan. The author interprets this fact as showing that the prize-winners have recognized that the plan is a good one for them.
Identify and Describe Flaw
The author assumes that the reason the winners have the Acme plan is that they believe the plan is a good one for them. This overlooks the possibility that they have the plan for some other reason unrelated to their perception of the plan’s quality. The author also assumes that if the winners believe the Acme plan is good for them, then that constitutes evidence that the plan actually is good for people with similar retirement needs.
A
It ignores the possibility that the majority of Economic Merit Prize winners from previous years used a retirement plan other than the Acme plan.
This possibility does not undermine the argument because prize-winners with other plans might simply have different retirement needs from the prize-winners the author cites to. Also, the author does not assert that the Acme plan is the best, or that it is the only good plan.
B
It fails to address adequately the possibility that any of several retirement plans would be good enough for, and offer a financially secure future to, Economic Merit Prize winners.
This possibility does not undermine the argument because the author does not assume that the Acme plan is the best. He states only that the prize-winners recognize that the Acme plan is “probably a good plan” for people wit similar needs. But there can be other good plans, too.
C
It appeals to the fact that supposed experts have endorsed the argument’s main conclusion, rather than appealing to direct evidence for that conclusion.
The main concluson is that the Acme plan is probably a good plan for anyone with retirement needs similar to those of the prize-winners. The author does not state or assume that the prize-winners endorse that specific conclusion.
D
It takes for granted that some winners of the Economic Merit Prize have deliberately selected the Acme retirement plan, rather than having had it chosen for them by their employers.
The author assumes that the reason some prize-winners have the Acme plan is that they perceive it to be good for them. This requires that the plan was not forced upon them. If it was, then the the fact some of them have the Acme plan does not tell us about their perception of it.
E
It presumes, without providing justification, that each of the Economic Merit Prize winners has retirement plan needs that are identical to the advertisement’s intended audience’s retirement plan needs.
The author’s conclusion is limited to “anyone with retirement needs similar to [the prize-winners’].” This acknowledges that some people might not have identical retirement needs.
Summarize Argument: Phenomenon-Hypothesis
Scientists hypothesize that P-fat is necessary for developing eyesight. This is because babies fed formulas low in P-fat have worse eyesight than babies fed mother’s milk, which is high in P-fat. Moreover, premature babies have worse eyesight than babies carried to term.
Notable Assumptions
The scientists assume that P-fat is the only relevant difference between formulas and mother’s milk. If there was some other difference, then that difference could just as well account for the difference in eyesight. The scientists also assume that babies carried to term receive more P-fat than those born prematurely.
A
Adults whose diets lack P-fat tend to have worse eyesight than those whose diets are high in P-fat.
We’re talking about developing eyesight. We don’t care about maintaining eyesight.
B
A fetus typically receives high levels of P-fat from the mother during only the last four weeks of pregnancy.
Premature babies have worse eyesight than babies carried to term because they miss out on a critical fetus stage: the last four weeks, where fetuses receive high levels of P-fat. This strengthens the connection between P-fat and developing eyesight.
C
Babies whose mothers have poor eyesight do not tend to have poor eyesight themselves.
The scientists agree eyesight isn’t totally genetic. However, we’re specifically trying to strengthen the connection between P-fat and eyesight. This doesn’t do that for us.
D
Babies generally prefer mother’s milk to formulas low in P-fat.
We don’t care what babies prefer.
E
The eyesight of a fetus develops during the last trimester of pregnancy.
This weakens the scientists’ hypothesis. If eyesight develops during the last trimester, then the postnatal difference between formula and mother’s milk wouldn’t be relevant.