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Identify an entailment | Video lesson

Watch a demonstration of one way to approach questions that ask you to identify an entailment that would follow logically from a series of statements.

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Video transcript

- [Instructor] Let's read this question together. It asks, if the information above is true, which one of the following must also be true? Because we're being asked to file a claim that must be true, this is an entailment question. That means that the answer will absolutely follow from the statements in the passage. The four wrong choices will be a claim that either conflicts with the passage information, or claims that could be true, but don't have to be true. Pause your video now if you'd like to try this question on your own. Otherwise, let's go into the explanation. Okay, let's read the stimulus together. For entailment questions, we aren't trying to find a conclusion and its evidence the way we do with lots of other question types. Here, we have statements that we're meant to understand as fact, so it's really important to pay attention to any relationships that we see. A person with a type B lipid profile is at much greater risk of heart disease than a person with a type A lipid profile. In an experiment, both type A volunteers and type B volunteers will put on a low-fat diet. The cholesterol levels of the type B volunteers soon drop substantially, although their lipid profiles were unchanged. The type A volunteers, however, showed no benefit from the diet, and 40% of them actually shifted to type B profiles. When's the last time you talked to your friends about lipid profiles? Don't let yourself get distracted by ideas that aren't common or everyday because the LSAT is about structure and precision. Everything you need to answer a question is right in the passage. Let's look at what we're working with. If we look at the big picture here, we see two groups. People with type A lipid profiles, and people with type B lipid profiles. Okay, well we're given a relationship right away, which is that type B means you're at much greater risk of heart disease than type A. Totally okay to jot that down on test day so that you remember the relationship. Now, they were both put on a low-fat diet, both of these groups, so we're given the results. For B, they dropped in cholesterol level, but they had the same lipid profiles. What does that mean again? Draw the connections. It means they have the same risk of heart disease than they did before. For the group in type A, they showed no benefit from the low-fat diet, and then 40% of them actually shifted to type B profiles. Again, let's read actively. What does it mean that they shifted to type B profiles? It means that they now have a greater risk of heart disease than they did before. We have absolutely everything we need in order to answer the question. We broke down the statements and understood the relationships by connecting the dots and the definitions that we were given. Our only job is to now look at each choice and ask ourselves, does this have to be true based on the passage? Can I prove it using the information in the passage? A, in the experiment, most of the volunteers had their risk of heart disease reduced at least marginally as a result of having been put on the diet. Does everything in this choice have to be true? Well let's look at some of the more sensitive words in this choice. Let's start with most. Did most of the volunteers have their risk of heart disease reduced at least a little bit because of the diet? Maybe, but maybe not. Most is more than 50%, right? Let's see if we a make this choice false. The only numbers we know is that 40% of the type A volunteers increased their risk of heart disease, and that 100% of the type B volunteers had the same risk of heart disease than they did before. But we have absolutely no idea how many people were in each group. That means there's no way that we can infer anything about the results of most of the volunteers. We can eliminate, because A could be false. B tells us that people with type B lipid profiles have higher cholesterol levels on average than do people with type A lipid profiles. Well this phrase, on average, should stick out to us for further scrutiny. What did we learn from the passage about the average person? Absolutely nothing. We only learned about the people in this experiment. Not only that, but we were never given information about comparative cholesterol levels between the groups, so this choice could absolutely be false. C says, apart from adopting the low-fat diet, most of the volunteers did not substantially change any aspect of their lifestyle that would've affected their cholesterol levels or lipid profiles. Remember how we felt really skeptical of the word most in choice A based on the information in the passage? Well the same thing holds true here. We're never told anything about any of the volunteers' lifestyle habits, much less about most of the volunteers' lifestyle habits. This choice could be true or it could be false, but it definitely doesn't qualify as a must be true. D, the reduction in cholesterol levels in the volunteers is solely responsible for the change in their lipid profiles. What particular language stands out to you in this choice? Maybe your eye was drawn to solely responsible, which is a great starting place. That's a really definite and strong claim that nothing else besides a lower cholesterol could've changed the volunteers' lipid profiles. In fact, we can't even confirm that there's any relationship at all between the cholesterol levels and the changes in lipid profiles. We're just given the details and results at a study, so be careful if you were drawn to choice D, because its language is far stronger than what the passage represents. Well, that leaves us with E, so let's see why it has to be the answer. For at least some of the volunteers in the experiment, the risk of heart disease increased after having been put on the low-fat diet. Ah, take note of the language here. We had wrong choices that talked about most, and on average, but here we have the phrase, at least some, and that's really flexible language because it just means one or more. That's a nice, big, safe range. We also see no specific qualifier with the risk of heart disease increasing. It doesn't say that it doubled, or tripled, or increased dramatically. It just says increased. That could be a little bit, or could be a lot. It's a big range. Now, let's look at the truth of the statement based on the passage being true. Which specific volunteers is choice E referring to? Who had their risk of heart disease increased after being put on the low-fat diet? It was the 40% that we see at the end here. The ones that shifted from type A, which is lower risk of heart disease, to type B, which is higher risk of heart disease. That's it. That's our answer. To recap, for entailment questions, try to pay really close attention to definitions. Pay attention to connections between the terms, to the relationships that you see. Here, we saw four wrong choices that went farther than what the passage allowed. It can be really easy to get carried away sometimes and exaggerate what you're actually reading, or make assumptions that aren't supported. Stay really close to the language that you see. We didn't need to know anything about lipid profiles to tackle this question. We only needed to understand the relationships that were present. Finally, sometimes you'll have strong predictions for entailment questions, and sometimes you won't. In this case, we didn't. When you don't have a strong prediction, make sure that you're comparing each choice against the passage one by one. Ask yourself if you can prove the choice using information in the passage. If you can't, or if you feel like you really have to fill in some blanks to do so, then you've got the wrong choice.