A
Toothpaste containing fluoride is widely available in both the United States and Europe.
B
Nearly all dentists in the United States use dental treatments involving the application of fluoride directly to tooth surfaces.
C
Dental hygiene is typically taught in elementary school in both Europe and the United States.
D
On average, children in Europe receive dental checkups more frequently than children in the United States.
E
The diets of children in the United States are not generally worse for teeth than those of children in Europe.
This is a Strengthen question.
The difficulty of this question mostly comes from the attractiveness of the wrong answers and a complication to an otherwise simple argument form. Stripping the wrong answers away and simplifying the conclusion reveal a common recurring pattern. The stimulus contains a correlation premise followed by a causal conclusion. The correct answer choice precludes an alternate hypothesis. But like I said, the actual argument is more complex and the presence of four very attractive wrong answers also works to obscure the pattern.
The stimulus starts with a dentist reporting data from five studies. The data reveals that in Europe, the proportion of children with bad teeth is lower than in the United States. It also tells us that in Europe, water is not fluoridated, whereas in the United States, water is fluoridated. As you can see, this is the classic setup where a phenomenon is presented that correlates with another phenomenon. And we’re invited to infer a causal relationship. Naturally, we want to explain why children in Europe have fewer teeth problems. The stimulus conveniently tells us that in Europe, water is not fluoridated, whereas in the United States, water is.
A simpler version of this argument could have gone like this: Therefore, fluoridated water causes teeth problems for children. This would be the classic A (fluoridated water) is correlated with B (teeth issues), therefore A causes B.
The actual argument is a bit more sophisticated and relies implicitly on the contrapositive argument form. The assumption is that if fluoridated water prevented teeth issues, then the data would have shown healthier teeth in countries with fluoridated water. The data showed just the opposite. So therefore, the actual conclusion states that fluoridated water doesn’t prevent teeth issues.
The reason why the reasoning is vulnerable is the same reason why, in general, arguments of this form fail. Bad causal assumptions. “If fluoridated water prevented teeth issues, then the data would have shown healthier teeth in countries with fluoridated water” would be true only if all other causal factors have been controlled for. Clearly, that didn’t happen. The data did not come from anything resembling an ideal experiment. Rather, it came from observational studies. That means whatever differences between Europe and the United States that may be causally relevant to the health of children's teeth are acting on the outcomes.
Think about this in terms of Weaken. If we wanted to expose the vulnerability of the reasoning, we’d simply point out any causal influence that wasn’t controlled for that could have affected dental health. For example, we could have stipulated that in the United States, children eat a lot more candy, which rots teeth. If that's true, then we found an explanation of the difference in dental health between Europe and the United States that doesn’t suggest that fluoridated water is ineffective. Rather, it may well be that fluoridated water actually protects teeth but that preventative causal impact is being overwhelmed by the decaying causal impact of sugars. Kids in the United States have teeth issues in spite of fluoridated water.
If stipulating this to be true weakens the argument, then precluding it strengthens the argument. This is what Correct Answer Choice (E) does. It tells us that the diets of children in the United States are not generally worse for teeth than those of children in Europe. This generally precludes the entire class of food-related explanations of the difference in dental health of which my sugar explanation was just one specific example. By precluding the entire class of explanations, (E) does not prove the hypothesis to be true. But (E) does strengthen the argument by making the hypothesis just a bit more probable.
Interestingly, had the argument been simpler, that is, had the conclusion simply said that fluoridated water causes teeth problems for children, (E) would still work. In fact, it’d be even more obvious that (E) fit the cookie-cutter mold of precluding an alternative explanation.
A note about strategy under timed conditions. I tend to remind you that given the nature of strengthening and weakening questions that deal in a phenomenon hypothesis, it is difficult to anticipate what the correct answer choice will say. That is true in this question as well, which is why, in general, the best strategy is to use POE even though you’d be exposed to the mischief of the wrong answers.
Answer Choice (B) says nearly all dentists in the United States use dental treatments involving the application of fluoride directly to tooth surfaces. (B) can be eliminated simply by recognizing that the causal direction of fluoride pushes in the opposite direction. The conclusion says that fluoride doesn’t benefit dental health yet (B) implies, by appeal to relevant authority, that fluoride does benefit dental health. Clearly, this does not strengthen the argument. But it also doesn't weaken the argument either if you look closer at the details. Even if it's true that fluoride, when directly applied by dentists to tooth surfaces, is effective for treating dental problems, it still may be true that fluoride in water has no effect on protecting teeth.
Answer Choice (D) says that, on average, children in Europe receive more frequent dental checkups than children in the United States. Rather than precluding an explanation of the differences in dental health, (D) seems to be introducing one. If children in Europe differ from children in the United States in that European children receive more frequent preventative care, then that explains why they have better teeth. This is just like when we contemplated diet as the alternative explanation. If children in Europe had a healthier diet for their teeth or had more frequent preventative care for their teeth, the fact that they have healthier teeth may have nothing to do with the presence or absence of fluoride in their water. This would weaken the argument.
Answer Choice (A) says that toothpaste containing fluoride is widely available in both the United States and Europe. (A) is attractive because in form it looks like it's holding some potential causal factor equal and therefore precluding that factor from accounting for the observed difference in dental health. The problem, however, is in order for (A) to be preclusive, it needs some questionable assumptions.
First, notice that we are being baited to assume that wide availability implies equal usage in children. That is a very specific and arbitrary assumption. Wide availability of fluoride toothpaste in and of itself doesn't bear on the issue. What we actually care about is whether children in Europe and the United States use that widely available fluoride toothpaste to a comparable degree. (A) is silent about that phenomenon.
Second, even if we fixed this first problem, (A) still has another subtler problem. Imagine if the answer said that the use of fluoride toothpaste is comparable for children in the United States and Europe. That would seem to preclude the possibility that European children use more fluoride toothpaste than their American counterparts, and it's this extra usage that accounts for their healthier teeth. Yet this reasoning requires fluoride to be good for teeth when in toothpaste, yet useless for teeth when in water. That's an unwarranted assumption. It's not impossible, but it hardly seems reasonable to assume without evidence.
Answer Choice (C) says dental hygiene is typically taught in elementary school in both Europe and the United States. (C) is attractive in the same way that (A) is attractive. In form it looks like it's holding some potential causal factor equal and therefore precluding that factor from accounting for the observed difference in dental health. In this case, the potential causal factor is whether dental hygiene is taught in school. And (C) precludes the phenomenon where dental hygiene is only taught in elementary school in Europe and not the United States. The problem is that we don't care much about precluding this phenomenon. Because even if dental hygiene is typically taught only in elementary schools in Europe and not the United States, a lot of other causal assumptions need to be supplied in order for the observed difference in dental health to be explained. First, we need to assume that children enact dental hygiene behaviors that they learn in school because otherwise the mere instruction would have no causal impact on their dental health. Second, we also need to assume that just because American children don't learn dental hygiene at school, they don't learn it at all. That seems highly unlikely, since if they're not learning it in school, then parents would have extra incentive to teach dental hygiene at home.
Notice how Correct Answer Choice (E) doesn't suffer from the need to fill in these causal gaps with questionable assumptions. If the diets of children in the United States were generally worse for dental health, then that explains the observed difference in dental health.
Of the dinosaurs of the birdlike group called ornithomimids, the later ones had toothless beaks and weak jaw muscles. A fossil of the later ornithomimid species Gallimimus bullatus was found to have remnants of a comblike plate inside the beak. Such plates are found in modern ducks and geese, animals that strain small bits of food from water and mud. Paleontologists therefore hypothesize that G. bullatus fed by filtering food from water and mud.
Summarize Argument: Phenomenon-Hypothesis
The paleontologists hypothesize that G. bullatus fed by filtering food from water and mud. They support this by noting that a fossil of G. bullatus had a comblike plate in its beak, similar to those found in ducks and geese today, which use them to strain food from water and mud.
Notable Assumptions
The paleontologists assume that G. bullatus could feed by filtering food from water and mud, and that factors like a very dry climate or a different diet didn't interfere with this. They also assume that the comblike plate had no other potential purpose that would better explain its presence, and that G. bullatus and modern ducks and geese are relevantly similar in enough ways to make the paleontologists’ hypothesis likely.
A
Some dinosaurs with toothless beaks and weak jaw muscles are believed to have pursued small prey and to have eaten eggs.
This fails to address the paleontologists’ key claim that G. bullatus’s comblike plate is evidence that it fed by filtering food from water and mud, nor does it help to make this hypothesis more likely.
B
Toothless beaks and weak jaw muscles were not common to any dinosaur group other than ornithomimids.
Like (A), this ignores the paleontologists’ primary argument, which is about the comblike plate, not the toothless beaks and weak jaw muscles. Also, we already know that G. bullatus was an ornithomimid with a toothless beak and weak jaw muscles, so (B) is irrelevant.
C
Except for the comblike plates in their beaks, G. bullatus shared few anatomical features with modern ducks and geese.
This weakens the paleontologists’ hypothesis by suggesting that G. bullatus and modern ducks and geese are not physically similar apart from their comblike plates.
D
Most G. bullatus fossils have been found in sediments deposited in lakes, rivers, and other wet environments.
This strengthens the argument by affirming one of the paleontologists’ key assumptions. If G. bullatus fed by filtering food from water and mud, they must have lived near water and mud, so their fossils would likely be found there too.
E
Paleontologists have not found evidence that any dinosaurs other than G. bullatus had comblike plates.
We already know that G. bullatus did have comblike plates, and the argument is concerned with whether they also fed by filtering food from water and mud. Whether any other dinosaurs had comblike plates is not relevant to the argument.
A
Animals that are startled sometimes act in ways that appear irrational to human observers.
B
Young gazelles and gazelles that are not very healthy often stot when they become frightened by humans or by loud machines.
C
To animals that typically prey on gazelles, stotting is a signal of strength and ability to escape.
D
A healthy gazelle can usually detect the approach of a predator before the predator becomes aware of the presence of the gazelle.
E
While not able to run as quickly as gazelles, predators such as lions hunt effectively by hunting in groups and coordinating their attacks.
Advertisement: Omnicide kills more species of insects than any other insecticide. So Omnicide is the best insecticide for home gardeners, especially gardeners who cannot determine which insects are destroying their plants.
Summarize Argument
The ad concludes that Omnicide is the single best insecticide for home gardeners, both in general and especially for those who can’t tell which insects are destroying their plants. Why is Omnicide the best? Because it kills the widest range of insects.
Notable Assumptions
The ad assumes that the more species of insects you kill, the better your insecticide is for home gardeners.
A
Some of Omnicide’s competitors kill almost as many species of insects as Omnicide does.
“Almost as many” means “not quite as many.” This simply reinforces the ad’s premise: Omnicide kills the most species of insects.
B
Many insect species are beneficial to garden plants, and Omnicide kills most of these beneficial species.
This undermines the ad’s key assumption. Killing more species than other insecticides do could actually make Omnicide a worse option for home gardeners—especially for those who don’t know which species to attack—because using it indiscriminately will kill beneficial insects.
C
Merely protecting plants from attack by insect pests does not guarantee that the plants will be healthy.
The ad never suggests that using Omnicide will guarantee healthy plants—it just argues that Omnicide is the best option available.
D
Omnicide is more profitable for the manufacturer than most other insecticides made by the same company.
Irrelevant. How profitable Omnicide is for the manufacturer has no bearing on whether it’s the best insecticide for home gardeners.
E
Omnicide does not kill weeds or mammalian pests such as gophers, moles, and groundhogs.
The ad is purely focused on the best insecticide—that is, the best killer of insects. How it performs against plant or mammal pests is irrelevant. We also don’t know whether other insecticides perform any better against such pests.
This is a Weaken question.
The stimulus is an advertisement that states Omnicide kills more species of insects than any other insecticide. From that premise, the advertisement concludes that Omnicide is the best insecticide for home gardeners, especially the ones who can't tell which insects are harming their plants.
But just because an insecticide kills the widest variety of insects doesn't mean that that's the best insecticide. A gardener who wants to protect her plants only wants to kill the harmful insects. This means the assumption in the advertisement's argument is that Omnicide kills only the harmful insects. Now, if that assumption is true, then the argument is pretty great. Omnicide is killing the widest variety of harmful insects. A gardener who doesn't know which insect is harming her plant should get Omnicide because it casts a wide net and increases the chances of killing the mystery pest.
But if that assumption were false, then this argument is severely weakened. Correct Answer Choice (B) cuts against that assumption. It says many insect species are beneficial to garden plants and Omnicide kills most of them. This weakens the argument to the point of directly damaging the conclusion. (B) is so powerful that it actually supports the opposite of the conclusion. This isn’t something that a correct answer in a Weaken question needs to do, but it is something that frequently occurs. Just be mindful that while some answers overshoot the standard, it doesn’t mean that they’re setting the standard.
Answer Choice (A) says some of Omnicide's competitors kill almost as many species of insects as Omnicide does. This doesn't weaken the argument. If anything, this only explicitly confirms that the competitors do not kill as many insects as Omnicide does.
Answer Choice (C) says merely protecting plants from attack by insect pests does not guarantee that the plants will be healthy. This is irrelevant. It could have been relevant if the conclusion were about the general health of plants. If that were the case, then of course damage from insects is only a partial consideration. We would also want to control for things like sunlight, nutrition, soil conditions, etc. But the conclusion is just about protecting plants from harmful insects.
Answer Choice (D) says Omnicide is more profitable for the manufacturer than most of their other insecticides. This is a classic bait trying to attack an argument by attacking the source. It doesn't work. The strength of the reasoning doesn’t turn on the profits. It might explain why the company is advertising Omnicide as opposed to another of their products, but that’s not our job here.
Answer Choice (E) says Omnicide does not kill weeds or mammalian pests like gophers or groundhogs. Similar to (C), this is not relevant because the conclusion is just about protecting plants from harmful insects. Again, this could have been relevant if the conclusion were about protecting plants from harm in general. If that had been the case, then other weeds or mammalian pests would be relevant considerations.
He also assumes that reliance on computers isn’t actually keeping productivity losses from being even worse. But it’s possible computers are helping the situation, and productivity growth in computer-heavy industries is dropping for unrelated reasons.
The right answer must suggest that increasing reliance on computers actually does help productivity growth for individual businesses.
A
The industries that rely most heavily on computer technology have been burdened by inefficiencies that have substantially hindered their productivity growth.
B
Productivity growth in many less industrialized nations has also dropped substantially since the 1960s and 1970s.
C
Productivity growth in industries responsible for producing computer technology has increased substantially as computer technology has become more widespread.
D
Within any given industry, the businesses whose productivity growth has been greatest have been those that have invested most heavily in computer technology.
E
Within the next few years, recent technological advances will almost certainly make investments in computer technology among the most effective ways for any business to improve productivity.
This is a Weaken question.
This is a really difficult question. It's difficult in a way that's quite similar to how other questions are difficult. The test writers engineered a terrible argument that made a number of different kinds of questionable assumptions.
The argument proceeds from premises to conclusion and it also proceeds from a high-level phenomenon to a low-level phenomenon.
The first sentence tells us that productivity growth in industrialized nations has dropped substantially since computer technology became more widespread in the 60s and 70s. This is a correlational phenomenon at the level of nations. At the level of nations, we observe that the ones that have adopted computer technology have seen their productivity growth drop. Does that mean computer technology is what caused the decrease in productivity growth? We don't know. It could be or could be something else.
The next premise presents a phenomenon one level lower. We learned that in industries that rely most heavily on computer technology, productivity growth has dropped the most. I'll ask the same question here. Does this mean that computer technology caused the decrease in productivity growth? Again, we don't know. But the argument is edging towards precisely that causal hypothesis, that computer technology caused the decrease in productivity growth at the level of the industry and at the level of the country.
Now we get to the conclusion which is one level lower still. It says that a business that has increased its reliance on computer technology probably has not improved its productivity growth by doing so.
This conclusion rests upon that causal assumption: computer technology causes decrease in productivity growth (at the level of a business). And we've already talked about why that assumption is questionable. It's the classic correlation causation flaw. Just because two things are correlated doesn't necessarily mean that one of them caused the other. But even if you recognize this causal assumption, you might still be stuck between Answer Choice (A) and Answer Choice (D). This is why the question is difficult.
Answer Choice (A) says the industries that rely most heavily on computer technology have been burdened by inefficiencies that have substantially hindered their productivity growth. It sounds like (A) is providing an alternate hypothesis, an alternate cause to explain the slowdown in productivity growth for industries that rely most heavily on computer technologies. (A) says don't blame computer technologies. Rather, it’s these other things, these other inefficiencies that are truly responsible for the decrease in productivity growth. Doesn't this seem like it weakens the argument? It sure looks like it's cutting against the causal assumption that the argument needs.
Answer Choice (D) says within any given industry, the businesses whose productivity growth has been the greatest have been those that invested most heavily in computer technology. (D) also seems to be cutting against the causal assumption. After all, if it's true that computer technology causes a decrease in productivity growth for businesses, then we certainly would not expect to find what (D) is telling us to be true. In fact, we would expect to find the opposite. (D) exhibits a pattern in causal arguments: confirming the predictions of a causal hypothesis counts as evidence in favor and disconfirming those predictions counts as strong evidence against.
So how do we decide between (A), which seems to be providing an alternate hypothesis, and (D), which seems to be providing facts inconsistent with the causal assumption’s predictions?
That requires our recognition that there is something other than causal logic taking place in this argument. Notice the shift from high-level phenomena to low-level phenomena. We start at nations, then we talk about industries, and finally the conclusion talks about particular businesses. Where the premise talked about industries that rely most heavily on computer technologies, the conclusion picks out a business that may or may not even be part of that industry. There’s been a set change. We can use concrete examples to make this more tangible. Finance is an industry that relies heavily on computer technologies, so we can take the premise to mean that finance has experienced productivity growth slowdowns. The conclusion, on the other hand, is only about a business that has increased its reliance on computer technology. That could mean an investment bank, or it could mean a space company. This is a crucial gap between the premise about what's happening in industries versus the conclusion about what we expect happened in particular businesses. Because of this change in sets, it's not even clear that the causal forces at play for the industries (whatever they may be) are even relevant for the particular businesses the conclusion is talking about.
This is what makes Correct Answer Choice (D) much more relevant to the argument than (A). Even if it's true that at the level of the finance industry, the real explanation for the productivity growth slowdown has nothing to do with computer technology but rather has to do with these other inefficiencies that (A) talks about, the conclusion is still about businesses that may or may not even be in the finance industry. Offering alternative causal explanations at the level of industries may not even matter at the level of particular businesses if those businesses aren’t members of the industry.
This is not so for (D) because (D) is at the level of the businesses. The phenomenon (D) described is straight-up inconsistent with the assumption that a business’ investment in computer technology is bad for its productivity growth. If it’s true that within any industry, the businesses that most heavily invested in computer technologies also saw the greatest productivity growth, then something else explains the industry- and nation-level correlation.
Answer Choice (B) says productivity growth in many less industrialized nations has also dropped substantially since the 60s and 70s. Who cares? We already know that productivity growth in industrialized nations have dropped, and beyond that we know that the industries that rely most heavily on computer technologies have dropped, and so the argument goes on. The strength of the logic of the argument has nothing to do with what's happening in the less industrialized nations. Now, if you're thinking, “Well, productivity growth has also dropped in the less industrialized and therefore less computer-technology-dependent nations, doesn’t that mean there’s some other causal force at work? In other words, it is not computer technology that's responsible for the decrease in productivity growth for the industrialized nations since the less industrialized nations also experienced decreases.” If that’s the line of reasoning, then (B) is just a worse version of (A). For one thing, (A) offers an alternative cause, “inefficiencies.” (B) merely hints at the existence of some other explanation. More than that, (B) is at a level even further removed from that of businesses. (B) is talking about nations.
Answer Choice (C) says productivity growth in industries responsible for producing computer technology has increased substantially as computer technology became more widespread. (C) might be tempting because it's telling us that there are at least some industries that experienced increased productivity growth and there's a reason to assume that those industries rely on computer technology because they produce computer technology. But the problem here is that we have very good reasons to believe that these industries are outliers, that they are unrepresentative. We already know that for the last several decades, computer technologies have been increasingly adopted, so we would of course expect the industries that supplied those technologies to have experienced growth. But the fact still remains that the other industries, the ones that didn't manufacture the computer technologies but merely adopted them, those industries still experienced decreased productivity growth.
Answer Choice (E) says within the two years, recent technological advancements will almost certainly make investments in computer technology among the most effective ways for any business to improve productivity. This is a predictive statement about the future. It's not clear if what is stated here will come to pass. There is a high probability as signaled by “almost certainly,” but there is still a chance that this won't happen. But even if it does, what does that have to do with the past? The entire argument is situated in the past. It describes phenomena that have taken place in the past and it makes a conclusion guessing at what happened in the past. What will happen in the future cannot affect what has already happened in the past.