Objection's LSAT Tips - "Must Be True" Questions (LR)

General information:

Question type: Must Be True
Section: Logical Reasoning
Sample prompts:
- which of the following must be true?
- …which of the following follows logically from the above statements?
- …which of the following can be properly concluded from the above statements?
Average # per test since 2000: ~3

Subtype(s): Most Likely True
Key phrases:
- The statements above most strongly support...
- Which one of the following can be most reasonably concluded
Average # per test since 2000: ~5

Introduction

The “Must Be True” question type is one of the most straightforward problem types on the LSAT. It is much less ambiguous than some of the other problem types on the test, and it is a good place to begin studying. The “Most Likely True” variant introduces a bit more ambiguity and difficulty, but both are so conceptually similar that mastery of one should lead to mastery of the other.

“Must Be True” questions are asking you to draw a valid conclusion based on the information provided in the stimulus. No outside knowledge is necessary and even if what the stimulus states contradicts your real world knowledge, you must work within the confines of the stimulus. At times, the correct answer will merely be a repeat of something stated in the stimulus. Do not let this fool you. Other times, you will need to recognize an unstated premise or draw an unstated conclusion.

Consider the following very simple and completely made up stimulus: 1. People who fall down the stairs always break their left leg. Mary is a person and fell down the stairs.

You can conclude that Mary was injured. You can conclude that Mary broke a bone. You can conclude that Mary broke her left leg.

You cannot conclude that she did not break her right leg. You cannot conclude that she did not break her arm. You cannot conclude that she was pushed. Those things could very well be true, but they do not have to be true. “May be true” does not equal “Must be true.”

Method

Everyone thinks differently. There are many different methods to tackling problems. I can only teach the method that worked best for me. There are tons of other books on the subject. I personally recommend PowerScore’s Logical Reasoning Bible if you want a more in-depth explanation of the various techniques and nuances.

The key to “Must Be True” questions is recognizing what exactly is being asked for. It is imperative to remember that you are looking for what MUST BE TRUE. Not what could be true, nor what may be true, nor what should be true. Most problems I have seen with these questions types stem from failure to keep this fact in mind. If you find yourself justifying an answer with, “Well hm, this could be true if…”, then move on and look for a better answer.

There are typically two major approaches to this type of question: anticipation and diagramming.

Anticipation is when you anticipate potential answer choices before actually reading the answer choices. In the made up stimulus above, anticipation would have been thinking to yourself, “Mary must have broken her left leg because the initial premise (people who fall down the stairs always break their left leg) says so.” What you want to do is look for connections – implicit or explicit – between the premises in the stimulus. Your anticipated answers won’t always appear, but you’ll be surprised how often a more general or more specific version of your anticipated answer is the correct answer

To aid in this, I recommend reading the question stem before the stimulus. This will give you some idea of what you are looking for. This is just a personal preference, however.

Diagramming, on the other hand, would be actually writing out conditional statements and drawing a conclusion based on that. Again, using the example above, you could write:

People Fall Down Stairs >> Break left leg
Person Mary fell down stairs >> ?

Diagramming can be very helpful at times, but the preferred method is anticipation. Some problems will require diagrams due to their sheer complexity, but on the simpler examples like the one above, valuable time can be saved by simply anticipating inferences without diagramming

Note on the “Most Likely True” subtype: The difference here is that the answers won’t always be absolute. Oftentimes, the answer choices will be more general than in strict “Must Be True” questions. However, only one of the answer choices will be most supported. A lot of these questions deal with statistics, surveys, or scientific studies and ask you to infer a valid potential conclusion from the statistic or study.

Examples

Let’s work through a couple of problem types together:

Prompt: Due to James’ childhood, James does not know the moral difference between right and wrong. He only knows the difference between what is legal and illegal. When James committed a crime, he did not recognize the fact that it was an immoral act, even though he knew it was illegal.

Stem: From the statements above, which one of the following can be properly inferred?

A) James committed no offense that was not legally permissible

B) James did something that was immoral

C) Moral ignorance is inexcusable

D) James’ childhood could have provided better moral training

E) James could now be taught to see the moral differences between right and wrong Analysis: So you look at the stem, see “properly inferred,” and recognize it is a “must be true” question. What can you conclude here, without even reading the potential responses? The big thing you can (and should) conclude is that James committed an immoral act. Why? Because the stimulus says so when it says “…the fact that it was an immoral act.” Calling it a fact means just that: a fact. No time to get philosophical and debate whether all crimes are immoral. If the stimulus says it, it is true unless otherwise stated. In most cases, only anticipating one or two conclusions is fine. The key is to get you thinking logically, not necessarily identify the exact answer.

Once you have identified an inference or two in your head, move on to the answers. What do you know? Our anticipated response is one of the answer choices (B). Funny how that works out so nicely sometimes, isn’t it? But one thing I recommend while you are studying is to work on identifying and explaining why the other answers are wrong rather than why the right answer is right. Time consuming? Absolutely, but well worth it in the end. Answer A is incorrect because the stimulus comes right out and said his crime was illegal.

Answer C goes beyond the scope of the stimulus. Remember, work with what is given. C might very well be true, but it does not have to be true based on what is given in the stimulus.

Answer D again goes beyond the scope of the stimulus. It might be true, but it is not something that has to be true. The stimulus does not speak about the circumstances of James’ childhood, thus we cannot conclude anything about it.

Answer E again goes beyond the scope of the stimulus. Like C and D, this might be true, but it does not have to be true. James could very well be taught to see the differences between right and wrong, but we cannot conclude that based on anything given in the prompt.

Ah, if only life could always be this easy…

Let’s try a couple of more difficult “Must Be True” questions

Prompt: The number of Canadian adults who live in relative poverty – that is, who make less money than do 85% of Canadian adults their age – is steadily increasing according to four major studies conducted over the past 15 years.

Stem: If the finding reported above is correct, it can be properly concluded that

A) When four major studies all produce similar results, those studies must be accurate

B) Canadian adults have worked progressively less over the past 15 years

C) The number of Canadian adults who are not living in relative poverty increased over the past 15 years

D) Over the past 15 years, the number of Canadian adults who are rich has declined

E) The incidence of relative poverty in Canadian adults tends to increase as the adults get older

Analysis: Oooh, this one is a toughie. It is questions like this that make the LSAT nasty. This is a tough question to anticipate a conclusion, but it is possible. First, notice the question is about statistics. You can assume that the answer choice will in some way relate to those statistics. Another thing to notice – and this is big for later question types as well – is that the question tries to throw you off by using “number of Canadian adults” and then using a percentage. As you will see in later question types, the LSAT loves to mess with your head by confusing you with raw numbers and percentages.

So what can you conclude here? Think of it this way: relative poverty is being defined as someone making less than 85% of Canadian adults their age. This means that out of 100 people, there can only be 15 people living in relative poverty (which would leave 85, or 85%, making more money than they). Now, for the number of people living in relative poverty to increase, the number of people NOT living in relative poverty must increase as well. Why? Well let’s say hypothetically the number of people living in relative poverty went up to 30. There cannot only be 100 people in the population anymore, or else only 70 people (or 70%) would be making more money than those 30 people in relative poverty. Therefore, based on the definition of relative poverty we were given, the number of people NOT living in relative poverty must have increased. If the number of people in relative poverty increased to 30, then the population is now 200 (15% of 200 is 30), which means that there are 170 people NOT living in relative poverty. It sounds confusing and complicating and it is, but I promise with time and practice it will come to you. The LSAT just likes to be difficult.

Another way to do a problem like this if you really can’t wrap your mind around what is going on is process of elimination. This is good to use in a bind, and oftentimes a problem will have many answers that are so out there that it makes finding the right answer easy.

Let’s try that here:

A) The stimulus never speaks to this point. We assume the studies are correct because the question stem asks us to assume the findings are correct. It never says that they are correct because they all agreed. Beyond the scope of what is being argued.

B) This could be true, but working less is not the only cause of making less money. Furthermore, the amount people make may not have changed at all. What if a bunch of people moved in? They’re either going to join the 85th percentile (and bump more people into the relative poverty pool) or they’re going to themselves join the relative poverty pool. You are one or the other – neither is not an option

C) Ding ding ding.

D) This is the trap answer, but you must work within the confines of the stimulus. The stimulus never talks about rich people nor does it define rich people. The number of rich people could have declined, but that doesn’t mean they went right into relative poverty.

Process of elimination worked decently here. 3/5 answer choices were easily eliminated, leaving C and D. A little extra thought eliminated D, leaving you with C. Worst case scenario? You increased your odds at guessing correctly from 20% to 50%.

Now, let’s try a “Most Likely True” question: Prompt: Most people do not have every item they produce judged for quality, but each piece an artist completes is evaluated. That is why artists produce such high quality-works.

Stem: The statements above, if true, most strongly support which one of the following?

A) A piece of artwork completed by an artist is generally evaluated more strictly than the majority of items most people produce.

B) By having every piece of their work evaluated, some people are caused to produce high-quality work.

C) No other people produce higher quality work than do artists

D) Only artists have every item they produce evaluated for quality

E) Some people produce high-quality work in spite of the fact that not every item they produce is judged for quality

Analysis: This is a good example of what makes “Most likely true” questions tricky. Every single one of the answer choices above could be true, but only one of the answer choices is directly supported by the stimulus. That is the key. What could very well be true in the real world is irrelevant unless it is supported by the stimulus. Do not bring in outside knowledge in questions like this.

When you read this stimulus, you should identify the components. In this case, there are two premises and a conclusion. The initial premise is “Most people do not have every item they produce judged for quality.” The second premise is that “but each piece an artist completes is evaluated [in contrast to most people] .” The stimulus then concludes that this is why artists produce such high quality works. What you want to be doing is trying to find any missing link between the premises and the conclusion. You want to find the assumption which the conclusion is based on. You probably already have the assumption in your head – it’s just a matter of picking it out. What the conclusion assumes is that evaluation of each piece of work causes some people (artists, in this case) to produce higher quality works. That is the assumption that you want to keep in mind when looking at the answers.

Now let’s break down each answer:

A) This is a tricky answer and traps many people. This is wrong for two reasons. The first (and biggest) reason is that this answer mentions the extent (more strictly) with which things are evaluated whereas the stimulus never talks about that. The second is that, even if you get rid of the word ‘strictly,’ this answer choice says that artists are evaluated more than the majority of items most workers produce. The stimulus just says that most people don’t have every item they produce evaluated – they may still have the majority evaluated.

B) Looks a lot like our anticipated answer, doesn’t it? This answer explicitly states the implicit assumption in the stimulus. This is our winner

C) This is wrong because it compares the work of artists to the work of other people. The stimulus never does this. It simply says artists produce high-quality work, not the “highest-quality” work.

D) The stimulus says “most people” do not have every item they produce judged for quality. The stimulus does not say “all people except artists” do not have every item they produce judged for quality. The word only is such a strong word that if even one exception exists then it is false. Terms like “only” and “all” are usually not correct because of this. This stimulus doesn’t say that no other groups go through the same evaluations artists do.

E) This could be true, but the stimulus does not talk about the quality of work produced by most people. It only talks about the quality of work of artists. This is another tricky answer and something that in the real world is most likely true, but based on the stimulus, this cannot be concluded.