This is an Inference question. The question stem says “properly inferred.”
This question contains two sets of information, one of which is irrelevant and the other of which is what generates the inference. This question is actually closer to an MSS question than an MBT question. This is rare. Most questions that contain “inferences” in the stem are logically tight. This question is conspicuously an exception.
The stimulus states that “most cats like to go outside to play when the temperature is above freezing.” Translating this statement into logic, notice the conditional indicator "when" and the quantifier "most." For conceptual simplicity, let's kick the sufficient condition up into the domain. We are now talking strictly within the domain of when the temperature is above freezing. Under that domain, we are saying that of the set of cats, most of them like to go outside to play. Again, all of this is under the domain of when the temperature is above freezing. Now, as it turns out, and there's no way you could know this beforehand, this statement is completely irrelevant. The only way you’ll realize this is when you consider the answers. None of them make use of this statement.
The next statement creates a conditional chain from which we infer the correct answer. We are now talking about a specific cat. Jamil does not allow his cat to go outside unless at least one member of his family is outside. Translating this unless statement, we get the conditional that if Jamil's cat is allowed to go outside, then at least one member of his family is outside. Next we learned that Jamil's family members go outside only when the sun is shining or it is hot outside. This conditional connects directly to the previous one. If at least one member of his family is outside, then it must be either that the sun is shining or it is hot or both:
J’s cat allowed outside → J’s fam member outside → sun or hot
Now we can run a contrapositive. If the sun is not shining and it is not hot outside, then no member of Jamil's family is outside, then Jamil's cat is not allowed to go outside.
Does that mean Jamil's cat is not outside? This is the space between a reasonable or “proper inference” versus a deductively valid, must be true inference. In order to draw the conclusion that Jamil's cat is not outside, we have to assume that if Jamil's cat is not allowed to go outside, then it is not outside. This assumption is what Correct Answer Choice (E) requires. The fact that this is the correct answer reveals that the test writers think “properly inferred” is a lower standard of proof than “must be true.” Or the test writers made a mistake, though that’s highly unlikely.
I said at the beginning that this question was unusual because the overwhelming majority of questions using the “properly inferred” standard deliver answer choices that meet the higher “must be true” standard. But just because the test writers tend to overshoot a lower bar doesn't mean that the bar has been raised. They are just overshooting what has always been and presently is a lower bar. This is the same lesson we draw from some easier Weaken questions where the correct answer is identical to the ideal answer. That’s just the test writers overshooting the bar. On harder Weaken questions, we see the correct answer requiring assumptions.
The more salient decision for you is strategy: what to do under timed conditions? How do you respond when you detect this gap? The same as you always do. You pick the best answer. Looking at the other answers will reveal that (E) is the best out of the bunch for having made the fewest assumptions.
Answer Choice (A) says if Jamil's cat is outside, then the temperature is above freezing. This answer makes exactly the same assumption that (E) makes, namely that if Jamil's cat is outside, then he was allowed outside. But in addition it makes a mistake in logic. If Jamil's cat is allowed to go outside, then either the sun is shining or it is hot outside or both. It's possible that the temperature is not above freezing because the sun could be shining.
Answer Choice (B) says if Jamil's cat is not outside, then something something. At this point you can stop reading because (B) makes a logical mistake, the oldest mistake in the book: sufficiency-necessity confusion. Jamil's cat not being outside can only be a necessary condition according to the chain we have above.
Answer Choice (C) makes the same logical mistake as (B): sufficiency-necessity confusion. The sun is shining or it is hot outside is at the tail end, the necessary condition end of the chain. You cannot start a sufficient condition with the sun is shining or it is hot outside. It leads nowhere.
Answer Choice (D) says if at least one member of Jamil's family is outside, then Jamil's cat is outside also. This answer also requires the same assumption that (E) requires. Notice it also says the cat is outside as opposed to Jamil's cat is allowed outside. Additionally, (D) makes a sufficiency-necessity confusion. If Jamil's cat is allowed to go outside, then at least one member of his family is outside, not the other way around.
This is a Must Be True, Except question.
Four answers must be true on the basis of the information in the stimulus. The correct answer could be false.
The stimulus tells us that wildlife experts are adding lime to water to counteract the harmful effects of acid rain. How exactly does lime help? First, it neutralizes acid and thus prevents some damage. Second, it also helps to restore the health of some lakes where life has already been damaged by acid. Note the causal language, not that this affects the correct answer.
Next, specific details about this treatment. If a lake is treated with lime, this treatment must be periodic. That’s a conditional claim. Why? Because water in the lake is constantly being replaced and that has the effect of carrying away whatever lime we put in there. That’s a causal claim. How periodically? That we don't know. But we are told that if a lake's water is replaced more than once every six months, then we're not going to use lime because it's too expensive. That's another conditional claim followed with a causal explanation. This makes sense because the more frequently water in the lake is replaced, the more frequently we have to add lime to it. The lakes where the water is being replaced more than once every six months are apparently too expensive.
Answer Choice (A) says if the lake is a candidate for liming, its water is replaced every six months or less often. This must be true. This is simply the contrapositive of the last statement in the stimulus. Note that negation of “more often than once every six months” is “once every six months or less frequently.”
Answer Choice (B) says in some lakes, if liming is to be successful over the long term in counteracting the harmful effects of acid rain, liming must be repeated at intervals. This also must be true for it is simply a restatement of a conditional from the stimulus. The stimulus states lakes in which lime is used must be treated “periodically,” which just means “repeated at intervals.”
Correct Answer Choice (C) states unlimed lakes in which the water is replaced frequently are less likely to be harmed by acid rain than those lakes in which water is replaced infrequently. This is simply an appeal to our common sense. It is entirely unsupported by the information in the stimulus and therefore could be false. We know from the stimulus that acid rain damages lakes. We also know that adding lime helps to protect and restore those lakes. (C), however, talks about unlimed lakes. It tries to compare two different kinds of unlimed lakes, one where the water is replaced frequently versus the other where the water is replaced infrequently. (C) says the former is less likely to be harmed by acid rain. Again, no information above supports this statement. But our common sense wants to say this is true because we think that if water gets replaced, it should carry the acid away as well, which should be better for the health of the lake. That sounds reasonable and it may in fact be true in the world. But that is irrelevant. The question stem asked for valid support from the statements in the stimulus.
Answer Choice (D) says liming can be effective even if it is used after some life in a lake has been killed by acid rain. This must be true. It is simply what it means to “restore the health of some lakes where life has already been harmed by acidification.”
Answer Choice (E) says if a lake's water is replaced frequently, it may not be economical to attack the effects of acid rain there by liming. This also must be true. Depending on how frequently, it may in fact not be economical. And we know exactly how frequently because the stimulus tells us: more than once every six months.
This is a Main Conclusion question.
The stimulus contains an argument with many complications. It starts with other people's argument. OPA is a causal argument moving from a correlational premise to a causal conclusion. The author responds to OPA by pointing out the possibility of an alternate cause. She does so by pointing out another correlation that wasn't considered by OPA. She concludes that OPA wasn't well reasoned.
First, we learned that North Americans are becoming more lethargic. In the third sentence, we find out that North Americans are also consuming more fast food meals. This is the correlational phenomenon which OPA—“one researcher”—uses to support his causal conclusion in the second sentence. OPA concludes that fast food has an adverse effect (casual) on people's health. Note the assumption that lethargy is bad for health.
The author begins her argument with “however.” The first thing she tells us is that few lethargic adults exercise regularly. This is introducing another correlation. OPA told us that lethargy is correlated with increased consumption of fast food. The author is telling us that lethargy is also correlated with less exercise. But more than that, the author says this correlation is actually causal because lack of exercise can contribute to lethargy.
Now we get to the author's conclusion, which is that OPA delivered a weak argument. The lethargy studies do not settle the question of whether fast food is unhealthy. In other words, the correlation between lethargy and fast food isn’t dispositive evidence that fast food causes lethargy and hence poor health. Why? Because an alternative explanation of the lethargy studies is available through its correlative and causal relationship with exercise.
Note that the last sentence of the stimulus is in fact the main conclusion and it has a conclusion indicator “thus” preceding it. This is a good reminder that shortcuts don't always work. In general, we’re better off focusing on the fundamentals rather than playing mind games with the test writers.
Answer Choice (A) is a premise of the author's argument.
Answer Choice (B) states something new and therefore cannot be the conclusion. It says that high consumption of fast food is a health risk only when combined with a lack of regular exercise. Given the information in the stimulus, I have no idea if that's true.
Answer Choice (C) says the researcher’s data show that the consumption of fast food is not the main cause of poor health in North Americans. This might be tempting, but this isn’t the main conclusion. There is a big difference between something not being the main cause versus not knowing whether something is the main cause. The author's conclusion is simply that whether fast food is unhealthy isn't settled by the lethargy studies. That's a much more modest claim than what's present in (C), which says that it is settled and we know definitively that fast food is not the main cause of poor health. That's not what the author was trying to say. The author pointed out exercise simply to reveal OPA's failure to consider alternative causes.
Answer Choice (D) says the lethargy studies failed to consider one probable cause of lethargy. This is not exactly right. The author criticizes OPA for failing to consider one probable cause of lethargy. Both the author and OPA use the lethargy studies as a starting point. Neither criticizes that study.
Correct Answer Choice (E) says the researcher's conclusion was not adequately justified by the lethargy studies. This is exactly right, and if you map the language from this answer onto the content of the argument, you get a correlation-causation flaw. The researcher's conclusion is that fast food causes lethargy. The lethargy studies are what supply half of the correlation between lethargy and fast food consumption. The author is simply saying that the correlation between lethargy and fast food doesn't adequately justify the conclusion that fast food causes lethargy.
This is a Strengthen question.
The argument uses causation logic. The stimulus begins and ends with two parts of a hypothesis (a causal conclusion): first, that large trucks are not causally responsible, and second, that studded snow tires are causally responsible for ruts in the transportation official’s city.
Why should we believe this? The premises state that out of the many places that have roughly as much large truck traffic as the official’s city does and also a comparable amount of snowfall, only the few places that allow snow tires have ruts in them. This looks like the results of a controlled experiment. All else held equal, we toggle only snow tires. With snow tires, ruts. Without snow tires, no ruts.
What clearly follows from the premises is that snow tires are causally necessary since without them there are no ruts. What also follows is that large trucks are not causally sufficient since there are cities with large trucks but no ruts. Had the author reached either or both of those conclusions, the argument would be fine. But he reached a far less nuanced conclusion, one that shifted the causal blame entirely away from large trucks (yet we only know that large trucks are insufficient, not that they’re without any causal impact) and entirely onto studded snow tires (yet we only know that snow tires are causally necessary, not that they’re sufficient). Another way to understand why the argument is problematic is to consider the alternative hypothesis that also fits with the facts: both the snow tires and the large trucks have to act together to cause ruts.
Look again at the premises and notice that the facts so far fit with both the author’s hypothesis (snow tires only) and the alternative hypothesis (snow tires plus large trucks). That’s because large trucks were present in all the cities considered. We simply toggled on and off the presence of snow tires. With snow tires toggled on we find ruts, with snow tires toggled off we find no ruts. The only hypothesis excluded is the large truck only hypothesis, which is another way of saying that large trucks are not causally sufficient.
So how do we decide between the snow tires only and the snow tires plus large trucks hypotheses? Lucky for us, they make different predictions. In cities that have snow tires but no large trucks, the snow tires only hypothesis would predict ruts while the snow tires plus large trucks hypothesis would predict no ruts. Seeing what actually happens in those cities will help us decide between the two hypotheses.
This is exactly what Correct Answer Choice (C) does for us. It says that most of the places that allow snow tires yet don't have large truck traffic have ruts. This fact confirms the prediction of the snow tires only hypothesis and rules out the snow tires plus large trucks hypothesis.
Answer Choice (A) says large trucks are not allowed to have studded snow tires in many areas. This was close but also so very far. With a tiny tweak, (A) could also have ruled out the combination hypothesis. We just needed to say that in those areas that allow snow tires, large trucks are not allowed to have snow tires. That means the ruts observed in the stimulus in the cities that allowed snow tires definitely did not come from large trucks with snow tires, on the assumption that the large trucks were not in violation of this ordinance. It means that the ruts came from other snow-tired vehicles. That means it is the snow tires and not large trucks that are causally responsible for the ruts.
Answer Choice (B) says the number of ruts in the roads of the official's city has declined recently as the amount of large truck traffic has diminished. This correlational phenomenon is inconsistent with the causal hypothesis in the argument. If it's true that large trucks don't cause ruts then we wouldn't expect to see any difference in the number of ruts as large truck traffic either increases or decreases. Because (B) disconfirms that prediction, it weakens the argument.
Answer Choice (D) says some cities with even more truck traffic than the official's city also have ruts in their roads. This is useless because we don't know whether those cities allow snow tires.
Answer Choice (E) says most places that have little snowfall do not allow the use of snow tires. That makes sense. But it's not clear how this has anything to do with the argument. We don't know whether those places have large truck traffic nor do we know whether they have ruts in their roads.
This is a Weaken question.
This argument starts with a hypothesis-conclusion. We are supposed to believe that the rise of mega-bookstores in the 90s increased sales of bestsellers but decreased sales of literary books. Why should we believe this? The remaining three sentences are the premises. First we learned that in 1986, best-selling hardcovers accounted for 7% of all hardcover sales, but by 1996, 10 years later, best-selling hardcovers accounted for 14% of all hardcover sales. If the conclusion rested solely on this premise, then the argument would be pretty weak because surely there are alternative explanations. This premise only establishes that the mega-bookstores coincided with this change in proportion of best-selling hardcovers.
And so the argument continues with another premise that attempts to explain how the mega-bookstores caused this change. It says that mega-bookstores can offer deeper discounts than independent bookstores and that they offer their biggest discounts on best-selling hardcovers, which encourages their sales at the expense of literary works.
At this point, you might be thinking about two seemingly different considerations, one about alternative hypotheses since even with the final premise being true, there still exists alternative explanations for the data. The other consideration comes from recognizing that there is a part to whole or subset to superset assumption present.
Correct Answer Choice (C) reveals that these two seemingly different considerations both arise from the same issue. Let’s start with the perhaps more obvious consideration of part to whole. You may have noticed that the premises only talk about hardcover book sales whereas the conclusion talks about all book sales. And so (C) says in the 90s, the literary works increasingly had their initial publication in paperback editions rather than hardcover editions. That means the data in the premises about hardcovers isn't the whole story. Even if it's true that mega-bookstores encouraged more best-selling hardcovers at the expense of literary hardcovers, and even if it’s true that that strategy is what accounts for the 7% doubling to 14%, we’re still only talking about hardcovers. The conclusion could still be false, meaning literary books could have been selling just fine. People were simply purchasing paperback literary works.
And this leads to the alternative hypothesis. One way of explaining the phenomenon described in the 10-year period between 1986 and 1996, that is, the doubling of best-selling hardcovers from 7% to 14%, is the account offered in the conclusion, that the rise of mega-bookstores increased sales of bestsellers at the expense of literary books. But that's not the only story you can tell. Another hypothesis to account for the increasing share of hardcover bestsellers is simply that the non-bestsellers (the literary books) stopped publishing in hardcover. If that's the case, then everything the premises offer can still be true, the statistic is still what it is, it's still true that mega-bookstores offer big discounts on best-selling hardcovers, which encourages their sales and discourages other hardcovers, but now we no longer believe that sales of literary works overall suffered, because, again, what happened in hardcover isn’t the whole story.
Answer Choice (A) says bookstore customers are more likely to purchase a book that they have seen on a bestseller list than one that they have not. (A) reveals the causal effect of being on a bestseller list. It causes people to buy the book. But it's not clear how this is relevant to the argument. Surely the argument already assumed this. In fact, what would a “bestseller” be if not a book that appeared on bestsellers' lists?
Answer Choice (B) says in the 90s, bookstore customers' most frequent purchases were books written by authors who had already written at least one bestseller. Like (A), it's not clear how this is relevant. The argument never assumed that bookstore customers' most frequent purchases were by obscure authors. So pointing out that they weren’t doesn’t harm the argument.
Answer Choice (D) says by 1996 there were about 20% more titles in print than in 1986. So in other words, in the 10 years that passed, if we imagine the number of titles in print to represent an entire pie, then the whole pie got 20% bigger. But the premise already reported data as a proportion, that is to say, as a slice. In 1986, bestsellers accounted for a 7% slice of the whole pie. 10 years later, bestsellers accounted for 14% of the whole but larger pie. So, if 10 years ago, I gave you a 7% slice of a pizza pie and then 10 years later, I gave you a 14% slice of another same-sized pizza pie, then you’d have exactly twice as much pie. But if the second pizza pie was larger than the first, then you’re getting more than twice as much pie.
So, as much fun as it might be to think about getting more pizza, it doesn’t have any bearing on the argument. How is this supposed to affect the reasoning? And by the way, (D) talks about overall titles in print whereas the stimulus reported only statistics from hardcover titles, which is merely a subset of the total titles. In other words, the stimulus only talked about a subset of the whole pie.
Answer Choice (E) says books that are not expected to be bestsellers are featured more often in independent bookstores than in mega-bookstores. What are we supposed to do with this information? If anything, this information is consistent with the argument. The author already told us that mega-bookstores can offer deep discounts on bestsellers which encourage their sales at the expense of literary books.
This is a Weaken Except question, so that means four answers cut against assumptions that the argument made.
Usually when you see a Weaken Except question, that means the argument is especially bad because how else can there be so many assumptions for the answers to contradict? This argument is no exception. It really is bad. And it's bad for having made two different types of assumptions. This can be difficult to recognize. Another difficulty is the use of jargon and the reference to ratios. If it's one thing that LSAT students don't like, it's scientific jargon and math. Both are present here.
The first sentence states a causal relationship that occurs on Earth. On Earth, biological activity leads to, i.e., causes, a change in the ratio. So this is my advice about how to overcome the hurdle of jargon and also incidentally the hurdle of “math.” They don't matter. They don't matter because the rest of the argument and all the answer choices consistently reference the same “ratio.” So who cares what the ratio is called? All we need to focus on is the causal relationship, which is that biological activity causes a change in the ratio.
The next sentence tells us that a newly discovered meteorite, a rock, from Mars exhibits ratios found only in terrestrial minerals dating from before the beginning of life on Earth. The sentence takes a bit of parsing to understand. First, you have to understand that terrestrial minerals mean rocks on Earth. So, in other words, the ratio we find in this rock from Mars is similar to the ratio we find in rocks from Earth before there was life on Earth.
Now we get to the conclusion. The author concludes that it's unlikely life occurred on Mars.
I already said there are two different types of assumptions here. One is the assumption of analogy. This argument relies on reasoning by analogy because it assumes that the causal relationship on Earth of biological activity causing a change in the ratio would also be present on Mars. Would it? Mars and Earth are different places and those differences could mean that this causal relationship isn’t analogous. This is what Answer Choice (A) and Answer Choice (B) point out.
Answer Choice (B) says the effects of life on the ratio depend on a number of climatic and environmental factors with regard to which Earth and Mars differ. This is a very straightforward way of disanalogizing Earth and Mars. (B) tells us that biological activity isn't the only cause that's involved in the alteration of the ratio. Other causes matter too, like climatic and environmental factors, and those factors are different between Mars and Earth. So the ratio found in the Mars rock may not indicate the absence of life on Mars after all.
Answer Choice (A) is more subtle than (B) but also works on the argument’s reasoning by analogy. It says life forms that have a different effect on the ratio from that of life forms on Earth could have evolved elsewhere. This means that we shouldn't assume that Earth life forms’ effects on the ratio is universal. That means it's possible that different kinds of life forms could have evolved elsewhere and that those extraterrestrial life forms could have had a different effect on the ratio. This is an indirect way of suggesting that Mars and Earth are disanalogous. (A) is suggesting that if life had evolved on Mars, it's possible that Martian life would have had a different effect on the ratio.
Of the four answers that weaken the argument, these are the two that cut against the argument’s use of reasoning by analogy. They point out dissimilarities between Earth and Mars. (B) does this specifically and explicitly. (A) does this indirectly by suggesting that Earth and other places in general may be crucially dissimilar.
The other two answers that weaken the argument do so by cutting against a different assumption. That’s the assumption that the single Martian rock tells us something about the state of the Martian planet. If you think about it, it might occur to you that Mars is a big place and the meteorite is quite small by comparison. Is it true that the properties of that single rock reveal something about the entire planet? Well, that all depends on what properties of the rock we’re talking about and what characteristics of the planet we’re trying to figure out. In some ways, surely this rock is representative of Mars. But don't assume that it is representative of Mars in all ways. This is what Answer Choice (D) and Answer Choice (E) point out.
Answer Choice (E) says the current ratio on Mars is different from that at the time the meteorite left Mars. That means the ratio in the rock is not representative of the ratio on Mars today. That means this rock is not evidence of what has happened on Mars since it left the planet. Has life evolved in the intervening time? It’s unclear. (E) severely undermines the relevance of the only piece of evidence on which the conclusion is based by declaring the evidence to be chronologically unrepresentative.
Answer Choice (D) says that relatively few terrestrial mineral samples (rocks we find on Earth) contain ratios that would indicate the presence of life. This is a subtler way of calling out the representativeness of the rock from Mars. (D) says that if we looked at the ratios of rocks on Earth, we would find no signs of biological activity. Yet we know there is obviously plenty of biological activity on Earth. Therefore, this method of reasoning, that is, using the ratio found in rocks, is a poor way of figuring out whether there is life on Earth. This suggests that using this kind of reasoning might also lead to a faulty conclusion for Mars. I'm careful to say “suggests” because I recognize that this (meta) argument itself depends on an analogy between Mars and Earth. The crucial similarity assumed is that just like on Earth, even if there was biological activity on Mars, most of the rocks on Mars would not reflect that activity. That means there’s a good chance that this sample, this only piece of evidence we have, would also fail to capture the effects of life on Mars.
As you can see from the way these answers are structured, (B) and (E) are the more explicit refutations of the two assumptions in the argument. (A) and (D) are the subtler counterparts. They merely suggest that the assumptions are questionable.
Correct Answer Choice (C) says the ratio in the rock from Mars is the same as that on the planet as a whole at the time that the rock left Mars. This doesn't hurt the argument. This helps the argument, though only a little. Now we can be sure that this rock was representative of the ratio on Mars as a whole at some point in time. It doesn't guarantee that it's still representative of the ratio on the planet in the intervening time, as (E) points out, but it does at least partially patch up the issue of representativeness.
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.
This is a Strengthen question.
We’re asked to find support for the paleontologist's hypothesis, which is the conclusion of the argument.
Here we have an argument that presents phenomena followed by a hypothesis that tries to explain the phenomena. We start with the set of dinosaurs, then we move into the subset called ornithomimids, which are birdlike, then we move into a further subset called the later-ornithomimids, which had toothless beaks and weak jaw muscles. A fossil of one particular member of that subset called G. bullatus shows a comblike plate inside its beak. We know that in modern birds like ducks and geese, plates like that are used to strain small bits of food from water and mud. So the argument concludes with a hypothesis that G. bullatus also fed by filtering food from water and mud.
The phenomenon is that G. bullatus has a comblike plate, and the hypothesis explains the function of the beak: for feeding. Support also comes from a premise about modern ducks and geese. That means this argument also uses reasoning by analogy. Therefore, one assumption is that the functionality of the beaks on ducks and geese is relevant as evidence of their function on G. bullatus .
As with most Strengthen and Weaken questions where the stimulus takes the form of phenomena-hypothesis, it's hard to anticipate the right answer choice because there are so many different directions that the question can go. Usually, the best strategy is POE.
Answer Choice (A) says some dinosaurs with toothless beaks and weak jaw muscles are believed to have pursued small prey and to have eaten eggs. First, it’s not clear how this is relevant to G. bullatus. If we assume that the dinosaurs in this answer exhibit similar behavior to G. bullatus, then that's not good for the hypothesis. This reveals that dinosaurs with toothless beaks can feed in some other manner. But this is not an effective Weaken answer choice either precisely because we have no reason to assume that the dinosaurs in this answer exhibit similar behavior to G. bullatus.
Answer Choice (B) says toothless beaks and weak jaw muscles were not common to any dinosaur group other than ornithomimids. All this tells us is that toothless beaks and weak jaw muscles are good evidence that the creature belonged to ornithomimids. If we were trying to identify a particular fossil and it showed signs of toothless beaks and weak jaw muscles, then this information might be helpful. However, the phenomenon we’re trying to explain above is what functionality comblike plates had. (B) doesn't help resolve that issue.
Answer Choice (C) says that except for the comblike plates in their beaks, G. bullatus shared few anatomical features with modern ducks and geese. (C) stresses points of dissimilarity between G. bullatus and modern ducks and geese. Whatever it's doing, it's certainly not strengthening the analogous reasoning above. But it's also not weakening that reasoning either, at least not by much, because (C) doesn't tell us what the few anatomical features that are shared between the two are. It merely tells us that there are few that are shared while most are not shared. But what we really need to know in order to either weaken or strengthen the reasoning by analogy is not just the proportion of similar to dissimilar features, but rather exactly which features are similar or dissimilar, because only the relevant similarities and dissimilarities matter, not all of them.
Correct Answer Choice (D) says most G. bullatus fossils have been found in sediments deposited in lakes, rivers, and other wet environments. This is evidence that corroborates the hypothesis by empirically confirming a prediction. If it's true that G. bullatus fed by filtering food from water and mud, then one would predict that these animals lived near water and mud. And if that's true, then one would expect to find their fossils near wet environments.
This is not dispositive evidence that the hypothesis is true. It is just another piece of evidence that gives a bit more weight to the hypothesis. In other words, it strengthens. You can see this by changing the quantifier on this answer choice. If instead of “most,” it said “nearly half,” or “some,” then the weight of this evidence diminishes accordingly. In fact, if it said “none,” then this would disconfirm a prediction of the hypothesis, which would weaken the hypothesis. Now, you might have concerns in the back of your mind like, “Wait, we’re talking about fossils, and surely after tens of millions of years, the fossils moved around.” Those are legitimate concerns. But I think the answer choice largely takes care of that by telling us that the fossils were found in sediments deposited near wet environments.
Answer Choice (E) says paleontologists have not found evidence that any dinosaur other than G. bullatus had comblike plates. This is similar to (B). If the issue above was that of identification, like if we had to figure out what species a particular fossil belonged to, then (E) may be relevant. If G. bullatus is unique in having comblike plates, then finding a fossil with comblike plates is evidence that the fossil is one of G. bullatus. But this is not the issue in the argument above. Rather, the issue is about the functionality of the comblike plates.
This is an RRE question.
The stimulus begins by telling us that when a healthy gazelle is frightened by hunters in a truck, they run away quickly and efficiently and hide themselves. So that is not surprising. The next sentence is where the surprising phenomenon starts. Notice the word “but” that introduces the phenomenon. It says that when a healthy gazelle detects an approaching lion, it does this thing called “stotting.” Stotting is where it leaps really high into the air as it's running away. Stotting has two consequences: one is that it uses a lot of energy that could have been used in running away, and the other is that it actually draws the lion’s attention. So therein lies the puzzle. Why do gazelles stot?
As is generally the case with RRE questions, how surprising the phenomenon is lies on a spectrum which turns on the kinds of assumptions we bring into the facts. In general, we tend not to know very much about the subject matter being discussed. Because of that, we tend to bring in pretty naïve assumptions. So in this instance, the naïve assumption that we might bring in would be that gazelles wouldn’t exhibit behavior such as stotting, which draws attention of the predator and which uses energy that could have been better spent on running away. But if you ask a subject matter expert, like a biologist who studies gazelles, she probably won't have the same set of assumptions that we do. She might already know what the explanation is for stotting.
Anyway, we don't have to be subject matter experts. We just have to understand the scientific logic that underpins this question. That’s the logic of phenomenon and hypothesis, the logic of causation.
Correct Answer Choice (C) says that to animals that typically prey on gazelles, which is to say, lions and cheetahs, stotting is a signal of strength and ability to escape. Okay, so this being an answer choice, we have to take it to be true. The question is whether the truth of this phenomenon explains the above phenomenon. The answer is yes. If stotting signals to a lion that this gazelle is strong and has the ability to escape, then the lion, presumably, is less likely to pursue that particular gazelle. I say presumably because it’s not explicitly stated. But that's a fairly reasonable assumption.
Answer Choice (A) says that animals that are startled sometimes act in ways that appear irrational to human observers. This answer choice at best restates the phenomenon instead of explaining the phenomenon. First we should acknowledge that there is nothing irrational about gazelles running away when they are frightened by hunters, so this answer isn't talking about that phenomenon. So the only phenomenon left is the phenomenon of stotting. And, indeed, the only reason why the question stem says there's an apparent paradox is because stotting appears to be irrational. It seems irrational that a gazelle would waste energy and draw the predator’s attention. That’s what we’re trying to explain. But you can’t “explain” it just by saying it seems irrational. You haven’t explained anything.
Answer Choice (B) says that young gazelles and gazelles that are not very healthy often stot when they become frightened by humans or by loud machines. This is a common type of wrong answer in RRE. This answer choice presents a phenomenon that is consistent with the phenomenon above and is similarly in need of an explanation. Having read this answer, I still don't understand why healthy gazelles stot when they detect a lion. In addition to that, I now have to wonder why young and unhealthy gazelles also stot when they are frightened by humans or loud machines.
Answer Choice (D) says a healthy gazelle can usually detect the approach of a predator before the predator becomes aware of the presence of the gazelle. In this competition between predator and prey, it's an enormous advantage to be more sensitive to the other’s presence. This answer reveals that it's the prey that's more sensitive. Okay, so that means the gazelle enjoys the first mover advantage. It can start running away before the lion even realizes that it's there. But this still doesn't explain why the gazelle stots as it runs away, especially when we were already told that stotting draws the lion's attention to the gazelle. Why not just run away without stotting?
Answer Choice (E) says that lions cannot run as quickly as gazelles, but they can still be effective by hunting in groups and coordinating. This answer choice reveals more information about how lions hunt. But it doesn't explain why gazelles stot. This answer is inviting us to make an unwarranted assumption that somehow stotting thwarts the lions' coordinated group hunting efforts. I have no reason to believe that's true. It seems, in fact, more likely that not stotting, which is to say, just straight up running away as fast as you can without showing off, would be the more effective strategy to escape a coordinated group attack.
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.